J 




\ 



TREATISE 



ON 



THE STEAM ENGINE 



bV 

JAMES RENWICK, LL.D. 

PKOFESSOR OF NATURAI, EXPERIMENTAL PHILOSOPHY AND CHEMISTRY, 
IN COLUMBIA COLLEGE, NEW-YORK. 



NEW- YORK: 
G. & C. & H. CARVILL. 



1830. 



Pt.-I. 




\ 5 ^ l£» ^ 



Southern Bistrtcf of New -York, 31, 
BE IT REMEMBERED, That on the sixteenth day of September, in the year of onr 
Lord, one thousand eight hundred and thirty, and in the fifty-fifth year of the Independence of 
the United States of America, G. Sz C. & H. Carvill, of the said district, have deposited in this 
office, the title of a Booir, the right whereof they claim as proprietors, in the words following, 
to wit : 

"TREATISE ON THE STEAM ENGINE. By James Renwick, LL.D. Pro- 
fessor of Natural Experimental Philosophy and Chemistry, in Columbia Colleger 
New York. 

In conformity to the Act of Congress of the United States, entitled "An act for the en- 
couragement of Learning-, by securing the copies of Maps, Charts, and Books, to the authors 
and proprietors of such copies, during the time therein mentioned." And also to an act, enti- 
tled "An Act, supplementary to an Act, entitled an Act for the encouragement of Learning, 
by securing the copies of Maps, Charts, and Books, to the authors and proprietors of such co]pie8, 
during the times therein mentioned, and extending the benefits thereof to the arts of designing, 
engraving, and etching historical and other prints." 

FREDERICK J. BETTS, 
Clerk of the Southern District of New-York. 



K 



/ 






1 




LUDWIG & TOLEFREE, PRINTERS, 
Corner of Greenwich and Vesey-streets, New-York. 



'U) 






PREFACE. 



f 3 



The treatise which is now submitted to the public does not 
pretend to the merit of originaHty. All that has been attempted 
is to exhibit in a succinct, and as far as possible, popular form, 
the present state of our knowledge on the interesting subject of 
which it treats. From this the sole exceptions are the theories 
of the oan' * re action of the steam engine, and of steam-boats. 
To the former has been added the consideration of the physical 
circumstances that were left out of view in the investigations of 
Watt and Robison ; and the latter has been examined upon 
principles, that, so far as the author is aware, although of fre- 
quent application in other branches of practical mechanics, 
have never been taken into account in this particular case. 

Preparing the work for the American public, and as a sub- 
stitute for treatises either too expensive or too rare to be of 
frequent occurrence, the author has not scrupled to avail him- 
self of the labours of his European predecessors. The authors 
that have been most frequently consulted, are : Peclet, from 
whose Traiti de Chaleur much valuable matter has been drawn ; 
Farey and Tredgold ; while the researches of Stuart have been 
of great service in the compilation of the historical parts. 



IV PREFACE, 

The author has also derived much information, from the 
friendly aid he has received in various ways from the most 
eminerft manufacturers of the steam engine who were within 
his reach. To the West Point Foundry Association, to Mr. 
Allaire, and Mr. Sabbaton, of New- York, and to Messrs. Rush 
and Muhlenburg, of Philadelphia, he takes this opportunity 
to return his acknowledgments, for the liberal manner in which 
their practical knowledge has been laid open to him. 

To Captain Bunker, of the steam-boat President, and to 
Mr. R. L. Stevens, he has also been under obligation for the 
facts in relation to steam-boats, which he has adduced as the 
test of his theory. 

From Dr. McNiven, he has received important facts in rela- 
tion to the preliminary experiments of Fulton at Paris, and the 
first trial of his boat on the Hudson, at both of which that 
gentleman had the good fortune to be present. Had not the 
work been extended beyond the size originally intended, this 
communication would have been inserted entire in the appendix. 

Should the present work be successful in extending the 
knowledge of the principles and mode of action of the most 
important of the instruments by which the power of man is 
extended ; and particularly, should it have an influence of 
bringing into use those precautions and apparatus by which 
the risk to which human life is exposed, may be lessened, the 
object of the author will be fully accomplished. 

Columbia College, ) 
New- York, 30th August, 1830. J 



CONTENTS. 



CHAPTER I. 

MECHANICAL AND PHYSICAL .PRINCIPLES THAT ARK APPLICABLE TO 

THE CONSTRUCTION OF THE STEAM ENGINE. 

Division of Material substances. — Forces which determine the state 
in which they exist. — Fomis which all bodies are capable of assum- 
ing, — Difference in th^^ode of action of solids and fluids. — For- 
ces and Motion. — C^^es of Gravity, Inertia, Percussion, Oscilla- 
tion, and Gyration. — Motions found in natural agents, and in the 
parts of Machines. — Mechanical properties of fluids. — Specific 
Gravities. — Pressure of the Atmosphere and Barometer. — Heat and 
its efiects. — Thermometer. — Expansion of bodies by heat. — Specific 
Heat. — ^Latent Heat. — Evaporation. — Radiation of Heat. — Con- 
ducting Power of bodies. — Mode in which liquids carry off heat. — 
Cooling- effect of gases. — Distribution of Heat among the particles 
of a solid. 9 

CHAPTER H. 

COMBUSTION. 

Definition of Combustion. — Oxygen. — Flame. — Atmospheric Air. — 
Currents of Air produced by Combustion. — Increase of Weight in 
the process of Combustion. — Temperature of Flame, and modes of 
burning of Solids, Gases, and Liquids. — Difierent species of Fuel. — 
Properties and chemical nature of Fuel. — Carbon and Hydrogen. — 
Comparative value of different kinds of Fuel. — Parts of Furnaces. — 
Ashpit. — Grate. — Body of the Furnace. — Flues. — Chimneys. — 
Damper. — Furnace doors. • 43 

CHAPTER III. 

BOILERS. 

Materials of which boilers are constructed. — Figure of Boilers. — 
Strength and thickness of Boilers. — Apparatus for showing the 
level of the water. — Feeding Apparatus. — Proof of Boilers.— 
Safety Valves. — Air Valves. — Steam Guages.- — Self-regulating 
Damper. — Common Damper and Register. — Dangers arising from 
the fire-surface becoming bare of water. — Thermometer. — Plates of 
fusible metal. — ^Valves opening at the limit of temperature. — De- * 
posits of solid matter, and modes of lessening and removing them, — 
Steam-pipes. — Generator of Perkins. 67 



VI CONTENTS. 

CHAPTER IV. 

GENERAL VIEW OF THE DOUBLE-ACTING CONDENSING ENGINE. 

Of Prime Movers in general. — Principles of the action of Machines. — 
Modes of applying Steam as a prime-mover. — Application of Steam 
to the Double- Acting Condensing Engine. — Modes of removing 
VS^ater of Condensation and Vapour. — Modes of changing the re- 
ciprocating Retilineal Motion of the Piston-Rod into a reciprocat- 
ing circular motion. — Method of changing the reciprocating circular 
motion into a continuous one. — Mode of regulating the varying 
motion of the Engine, and making it produce one with uniform ve- 
locity. — Other methods of obtaining a rotary motion. — Effect of the 
joint action of two Engines. — Water used to produce condensa- 
tion. — Water that has been employed in condensation applied to 
feed the boiler. — Manner of ascertaining the state of the Vacuum 
formed by condensation. — Mode of regulating the supply of 
Steam. — Accumulation of Steam in the boiler, and mode of prevent- 
ing it. — Double-acting condensing Engine considered as self-act- 
ing, — Packing and Cements. — Estimate of the power of the double- 
acting Condensing Engine. — Estimate of the quantity of water 
evaporated for each unit of force. — Estimate of the supply of water 
for the boiler. Ill 

CHAPTER V. 

DESCRIPTION OF THE DOUBLE-ACTING CONDENSING ENGINE. 

Usual form of Double-Acting Condensing Engine. — Steam-pipe. — 
Jacket. — Side Pipes. — Slide Valve. — Puppet Valve. — Cylinder. — 

Cylinder Lid. Cylinder Bottom. Piston. — Woolf's Piston. — 

Cartwright's Metallic Packing. — Condenser. — Air Pumps. — Deli- 
vering door. — Air pump Bucket. — Hot Water Cistern and Pump. — 
Cold Water Cistern. — Injection Cock. — Water of Condensation. — 
Cold Water Pump. — Parallel Motion. — Lever Beam. — Pump Rods. 
Connecting Rod. — Crank. — Fly Wheel. — Tumbling Shaft. — Ec- 
centric. — Double Eccentric. — Adjustment of Eccentric. — Gover- 
nor. — Throttle Valve. — Other forms of Double-Acting Condensing 
Engine. — Mode of setting these Engines in motion. 141 

CHAPTER VL 

GENERAL VIEW OF CONDENSING ENGINES ACTING EXPANSIVELY, OF 
HIGH-PRESSURE, SINGLE-ACTING, AND ATMOSPHERIC ENGINES, PAR- 
TICULAR DESCRIPTION OF HIGH PRESSURE ENGINES. 

Regulation of steam by the valves of Condensing Engines. — Expan- 
sive force of steam, supposing the temperature to remain constant. — 
Expansive force of steam of a given tension and in a given engine, 
on the same hypothesis. — Expansive action of steam of a given 
tension and constant temperature, when the friction and resistance 



CONTENTS. VU 

are taken into view. — Expansive action at increasing tensions, and 
with temperatures varying according to the law of specific heat. — 
Effects of steam acting expansively, as usually employed. — Action 
of high pressure steam when not condensed. — Cases in which high 
pressure engines are useful. — Reconsideration'of the precautions to 
be used in boilers generating high steam. — General view of the high 
pressure engine, its steam pipes, side pipes, and valves. — Calcula- 
tion of the power of high pressure engines, their working beam, 
parallel motion, throttle valve, governor, and forcing pump. — 
General view of the single-acting condensing atmospheric engines. — 
Particular description of a high pressure engine, with a beam, and 
of long and short slide valves. — Particular description of a horizon- 
tal high pressure engine. 167 

CHAPTER VII. 

EARLY HISTORY OF THE STEAM ENGINE. 

Introduction. — Statue of Memnon. — Hero of Alexandria. — Eolipyle. — 
Anthemius and Zeno. — Cardan. — Mathesius. — Baptista de Porta. — 
De Causs. — Brancas. — Wilkins and Kircher. — Marquis of Worces- 
ter. — Hautefeuille. — Papin's first plan. — Savary. — Papin's Engine 
for the Elector of Hesse. — Newcomen and Cawley. — Potter's 
Scoggaji. — Beighton's Hand-Gear. — Smeaton. — Leupold. 195 

CHAPTER VIII. 

CONCLUSION OF THE HISTORY OF THE STEAM ENGINE. 

Power and Defects of Newcomen's Engine. — Birth and education of 
Watt. — Professor Robison. — Watt's first experiment. — Professor 

Anderson. — Watt's second Experiment. Inferences. Separate 

Condenser. — Steam applied as the moving power. — Packing. — Jack- 
et and Air Pump. — Working Model. — Dr. Roebuck. — Experimental 
Engine. — Watt's first patent. — Gainsborough's claim. — Boring ap- 
paratus. — Form of Watt's first Engine. — Saving of Fuel. — Pro- 
jects for rotary motion. — Fitzgerald, Stewart, and Clark. — Double- 
acting Engine of Watt. — Washborough and Pickard. — Crank. — 
Sun and Planet Wheel. — Other Inventions and Improvements by 
Watt.— Hornblower. — Watt's patent extended. — Governor. — In- 
troduction of steam into various mechanic arts. — Expiration of 
Watt's patent. — Cartwright and Sadler. — Murray, Maudslay, and 
Fulton. — Woolf. — Oliver Evans. — Trevithick and Vivian. — Rota- 
ry Engines. — Conclusion. 227 

CHAPTER IX. 

APPLICATIONS OF THE STEAM ENGINE. 

General view of the application of the Steam Engine. — Raising wa- 
ter. — Grinding corn. — Cotton Spinning. — Navigation. — Bossut's 



Vill CONTENTS, 

laws of the compact of fluids. — Principles of the action of Pad- 
dles. — Juan's laws of the action of fluids on solids moving in 
them. — Maximum speed of vessels. — Power required to propel 
paddles. — Relation between the power and the surface of the Pad- 
dles. — Laws of the motion of Steam-boats. — Theory of paddle 
wheels. — Comparison between theory and observation. — Practical 
Rules. — Steam-boat engines. — History of Steam navigation. — 
Application of Steam to Locomotion. — History of the Steam 
carriage. — Conclusion. 259 

APPENDIX No. I. 
On the tension of Aqueous Vapour by Messrs. Arago and Dulong. 301 

APPENDIX No. II. 
On the explosions of Steam Engines, by M, Arago. 309 

APPENDIX No. III. 
List of English Steam-boats. 319 

APPENDIX No. IV. 
List of French Steam-boats. 321 

APPENDIX No. V. , 
Table of the Dimensions of Enghsh Double-acting condensing En- 
gines. ^^^ 

APPENDIX No. VI. 
Table of the dimensions of American High Pressure Engines. 325 

INDEX. 327 



TREATISE, &c. 



CHAPTER I. 

MECHANICAL AND PHYSICAL PRINCIPLES THAT ARE APPLI- 
CABLE TO THE CONSTRUCTION OF THE STEAM ENGINE. 

Division of JVEaterial substances. — Forces which determine 
the state in which they exist. — Forms which all bodies are 
capable of assuming. — Difference in the mode of action of 
solids and fluids. — Forces and JWotion. — Centres of Gra- 
vity. Inertia, Percussion, Oscillation, and Gyration. — 
tMotions found in natural agents, and in the parts of Ma- 
chines. — Mechanical properties of fluids. — Specific Gravi- 
ties. — Pressure of the Atmosphere and Barometer. — Heat 
and its effects. — Thermometer. — Expansion of bodies by 
heat. — Specific Heat, — Latent Heat. — Evaporation. — Ra- 
diation of Heat. — Conducting Power of bodies. — Mode in 
which liquids carry off heat. — Cooling effect of gases. — 
Distribution of Heat among the particles of a solid. 

The material substances with which we are acquainted 
are either Solid or Fluid. 

Fluids are again subdivided into two classes, those which 
are incompressible, and those which are elastic : the former 
are called Liquids, the latter Aeriform Fluids. 

Elastic or aeriform fluids may either be capable of being 
readily condensed into the liquid form, and are then called 

2 



10 PRINCIPLES OF MECHANICS. 

vapours or steam ; or can only be reduced to that form with 
great difficulty, resisting in some cases all the means, 
whether mechanical or physical, that have hitherto been 
applied for that purpose. The latter are styled gases or 
permanently elastic bodies. 

The last named class may, however, when in chemical 
combination, assume both the liquid and solid form, and 
there are but few that have not, in recent experiments, 
been converted into liquids, by pressures of greater or less 
intensity. Still, however, although nearly the whole class 
are now known to be condensible, the distinction between 
vapours and gases may be here retained with propriety, 
inasmuch as there is a wide difference in the manner in 
which they are applied in practical mechanics. 

2. Two great antagonist forces are concerned in deter- 
mining, in which of these mechanical states a body shall 
exist : these are Attraction and Heat. To that species of 
attraction which takes place between the particles of one 
and the same body, whether it be simple, or compound, in 
its chemical character, the name of Attraction of Aggrega- 
tion has been given. When the intensity of the attractive 
forces, exerted mutually by the particles of a body, is 
greater than the action which heat exerts to separate them, 
the body will exist in the solid state ; when the action of 
attraction and heat exactly balance each other, the body is 
a liquid ; and when the repulsive force of heat predomi- 
nates, the body passes into the state of an elastic fluid. 

We know, however, of no perfect hquids ; in them all 
there remains a greater or less preponderance of the attrac- 
tion of aggregation. This is manifested by the tendency 
they have, when minutely divided, to form small globular 
masses, or drops. And hence the motion of their particles 
among each other, meets with a slight resistance, which is 
said to be due to the viscidity of the fluid. 



PRINCIPLES OF MECHANICS. 11 

3. It may be considered as a general rule, that all bodies 
in nature are capable of existing, when properly influenced 
by heat, in either of the three mechanical forms. Thus, if 
we cannot, by mechanical or physical means, reduce the 
the lighter gases to the solid form, still we find them assum- 
ing it in chemical combinations ; while nearly all, even of 
the most refractory solids, have been melted and rendered 
volatile under the intense heat of the Galvanic Deflagrator, 
or of the Compound Blow-pipe. 

4. The general principles of mechanics apply equally to 
solid and fluid bodies, but are modified in their action by 
the peculiar nature of each. Solid bodies, having their 
particles firmly connected together, act as if all the matter 
they contain were collected in a single point. When the 
body presses merely by its own weight, or when the motion 
is rectilineal, this point is the Centre of Gravity, or of Iner- 
tia ; if the body oscillates around a fixed point, it is 
the Centre of Oscillation or Percussion ; and when it re- 
volves around an axis, it is the Centre of Gyration. The 
properties of these points, along with the general principles 
of motion, and the causes that produce it, are of constant 
value in considering the structure of the steam-engine and 
its parts. And although these are to be found in all books 
on the theory of mechanics, it has been considered proper 
to recapitulate them in a succinct manner, in order that 
they may be referred to in the course of the work. 

5. The cause which would tend to set a body in motion, 
whatever be its nature, is called a force. 

A body moves in the direction of the force impressed, and 
with a quantity of motion equal to the intensity of the force. 

A body set in motion by a force and then abandoned to 
itself, would continue to move uniformly forwards in a 



12 PRINCIPLES OF MECHANICS. 

straight line, were not its direction and the intensity of its 
motion to be changed by the action of other forces. Thus, 
near the surface of the earth, the friction of other bodies, 
and the resistance of the air, act continually to retard and 
finally destroy the motion of bodies, while the attraction of 
the earth constantly tends to change the direction of the 
motion, and bring the body back to the surface. 

When a body is set in motion by a force which acts du- 
ring the whole continuance of the motion, it will still de- 
scribe a straight line, but the spaces described in equal 
times will gradually increase. If the force act with equal 
intensity upon the body, whether it be in rest or in motion, 
the motion is uniformly accelerated, and the force is said 
to be constant. All forces that act continually, whether 
constant or not, are called accelerating forces. 

When more than one force acts upon a body at the same 
instant of time, the direction and intensity of the motion 
will depend upon the joint action, and we may imagine it 
to be the effect of a single force, whose direction and in- 
tensity correspond with the motion given to the body. 
Such a force, which, were the forces that really act with- 
drawn, would produce the same effect that they do, is 
called their Resultant ; the forces that it would thus iden- 
tically replace are called the Components. 

The resultant of two forces that act in the same straight 
line, and in the same direction, is equal to their sum ; if in 
the same straight line, and in opposite directions, it is equal 
to their difference : generally, the resultant of any number 
of forces acting in the same straight line is equal to their 
algebraic sum^ the difference of direction being denoted by 
the use of the positive and negative signs. 

The resultant of two forces whose directions are inclined 
to each other, and which meet in a point, is represented in 
magnitude and direction by the diagonal of a parallelogram 



PRINCIPLES OF MECHANICS. 13 

whose sides represent the direction and magnitude of the 
forces. The resultant of three forces is found, hy taking 
first the resultant of two of them, and then combining this 
resultant with the third. The resultant of three forces thus 
found may be combined with a fourth, in order to find the 
resultant of four, and so on for any number of forces. 

When in a machine a force acts obliquely, no more of 
the force is effective than that, which would be a compo- 
nent of the force in the line of direct action ; the other 
component is a loss of power, so far as the mechanical ef- 
fect to be produced is concerned. It is, however, in gene- 
ral worse than a mere loss of power, for the whole of the 
force decomposed in this last direction acts upon the ma- 
chine itself, and generally to wear away or dislocate its parts. 

Motions are capable of being resolved or decomposed in 
the same manner as forces, and the investigation may in 
this way be extended to the case of forces that continue to 
act during the whole duration of the body's motion. 

A motion which grows out of the combination of two 
other oblique motions, is in the direction of the diagonal of 
the parallelogram whose two sides represent the magnitude 
and direction of the two forces, and the intensity of the 
motion is represented by the magnitude of the diagonal. 
When two oblique forces act, one of which abandons the 
body, and would thus produce an uniform motion, while the 
other continues to act during the whole duration, we con- 
ceive the motion to be divided into a great number of very 
small portions, during each of which the motion and direc- 
tion remain constant : the body would then tend to go on 
in a straight line, at the end of each of the small intervals 
in which the small portions of the motion are performed, 
but is, during each of them, deflected into the diagonal of 
a parallelogram by the active force. In this way a polygon 
is formed, which, as the sides are inappreciably small, coin- 



14 PRINCIPLES OF " JHANICS. 

cides with a curve. When, therefore, two motions oblique 
to each other are combined, one of which is uniform and 
the other accelerated, curvilinear motion is the conse- 
quence. 

If two accelerating forces act, in which the rate of accel- 
eration is the same, the motion is rectilineal ; but if it be 
different, the motion is still curvilinear. 

When two parallel forces act upon a body, the resultant 
divides the line that joins the points to which the forces are 
applied, into parts that are inversely proportioned to the 
intensity of the two forces, and the resultant is equal in 
magnitude to the sum of the forces. The resultant of three 
such forces is found by taking first the resultant of two of 
them and combining it with the third ; this may again be 
combined with a fourth, and so on to any number. 

The resultant of any number of parallel forces continues 
of the same intensity, and passes through the same point, 
whatever be the direction of the forces ; hence it is called 
the Centre of Parallel Forces. When the body is moving 
forward in a straight line, under the action of forces other 
than gravity, it is called the Centre of Inertia ; when the 
body is acted upon by gravity, it is called the Centre of 
Gravity. 

6. By gravity, or the attraction of gravitation, is meant 
that force, by virtue of which all bodies fall towards the 
earth, in lines perpendicular to its surface. Although 
these directions are neither absolutely parallel, nor the 
forces, at different parts of the earth, or different distances 
from its surface, equal ; still the convergence of the lines is 
so small, and the variation so slow, that there is no impropri- 
ety in considering every particle of the body as acted upon 
by an equal and parallel force. The resultant of all these 
forces is the Weight of the body, and its place of action is 
the Centre of Gravity. 



PRINCIPLES OF MECHANICS. 15 

When the centre of gravity is supported, the body is 
supported also ; when the centre of gravity is not support- 
ed, the body will fall until the centre of gravity reaches the 
lowest possible point. The supporting force may be ap- 
plied to the centre of gravity, or it may act at a point 
vertically above, or vertically beneath that centre. In the 
first case the position of the body is indifferent, and it will 
remain at rest, however placed around the point of support; 
in the second case, the body, if once disturbed, will fall or 
move around the point of support, until this be vertically 
above the centre of gravity ; in the third case, if the body 
be disturbed, it will oscillate until it return to rest in the 
position it originally held. 

The centre of gravity of a straight line bisects it. 

The centre of gravity of a cylinder, or of a spindle of 
symetrical form, bisects the axis. 

The centre of gravity of a circle corresponds with its 
centre, as does that of a sphere. 

The centre of gravity of a triangle is in the line which 
joins its vertex to the point that bisects its base, and at the 
distance of two-thirds of this line from the vertex. 

When the centre of gravity of a triangle is known, that 
of a quadrilateral figure may be determined by dividing it 
into two triangles, and finding their respective centres of 
gravity, whence the common centre may be determined, as 
it will divide the line that joins the two, into parts inversely 
proportioned to the size of the two triangles. The centre 
of gravity of a pentagon is found by dividing it into three 
triangles, and thus for any polygon whatsoever. 

The centre of gravity of a triangular pyramid is in the 
line which joins the vertex of the pyramid to the centre of 
gravity of the base, and at a distance of three-fourths of this 
line from the vertex. 

When the centre of gravity of a pyramid is determined 



16 PRINCIPLES OF MECHANICS. 

we have the means of finding that of any solid body bound- 
ed by plane surfaces, for it may be divided into triangular 
pyramids. 

The centre of gravity of a solid cone is in the line which 
joins its vertex to the centre of its base, and at the distance 
of three-fourths of that line from the vertex. But the cen- 
tre of gravity of the surface of a cone is at the distance of 
two-thirds of that line from the vertex. 

The centres of gravity of an ellipsis and an ellipsoid of 
revolution correspond with their respective geometric cen- 
tres. 

When a body is attached to a fixed point and oscillates, 
the action is no longer such as would take place if the 
whole of the matter were collected in the centre of gravity, 
but the point, in which, if all the matter were collected, 
the action would be the same as actually takes place is 
farther from the place of suspension ; this point is called 
the centre of oscillation. 

The centre of oscillation of a straight line is distant two- 
thirds of its length from the point of suspension. 

The centre of oscillation of a triangle is at a distance of 
three-fourths of its height from the vertex. 

The centre of oscillation of a cone, right angled at the 
vertex, is in the middle of the base. 

The centre of percussion is that point in a striking body, 
at which the whole of the motion would be communicated 
to the body struck. 

When the striking body moves round a fixed point, the 
centre of oscillation and centre of percussion are identical. 

A body suspended from a fixed point, and oscillating un- 
der the action of gravity, is called a Pendulum. 

The Centre of Gyration is that point in a revolving body 
in which if all the matter were collected, the quantity of 
rotary motion would remain the same as before. 



PRINCIPLES OF MECHANICS. 17 

The centre of gyration of a straight line, moving around 
an axis passing through one of its extremities, is at a dis- 
tance from that axis, which bears to the length of the line 
the ratio of one to the square root of three, 1 : s/^» 

The distance of the centre of gyration of a circle or 
circular sector from its centre of rotation and curvature, 
is to the radius of the circle, as one to the square root of 
two, 1 : V2 

The motions which we find in the parts of machines, and 
in the great natural agents that are employed to propel 
them, are either rectilineal or rotary. Rectilineal motion 
may be either continuous or reciprocating, and rotary mo- 
tions may in like manner either go on continually, or the 
moving points may oscillate within certain limits, and thus 
reciprocate. 

Among these four species of motion, taken by pairs, 
there are ten possible combinations, and these might there- 
fore occur in the changes which a machine makes upon the 
original motion of the moving power, or which one part of 
a machine causes in the motion of another ; but eight of 
these combinations, however, are to be met with in practice. 

a. A continuous rectilineal motion is sometimes convert- 
ed into another continuous and rectilineal motion, in an 
opposite direction, 

6. A continuous rectilineal motion is sometimes changed 
into a continuous rotary motion, or, 

c. Into a reciprocating rotary motion. 

d. A continuous circular motion is sometimes changed 
into an alternating rectilineal motion. 

c. A continuous circular motion is sometimes changed 
into another continuous circular motion, in an opposite 
direction, or, 

/. Into a reciprocating circular motion. 

3 



18 PRINCIPLES OF MECHANICS. 

g". A reciprocating rectilineal motion is sometimes 
changed into a reciprocating circular motion. 

h. A reciprocating circular motion is sometimes changed 
into another reciprocating motion in an opposite direction. 

8. The particles of fluid bodies, having no, or at most an 
insensible, attraction of aggregation, act independently of 
each other. Hence, we cannot refer the motion of a fluid 
mass to either of the Centres of which we have spoken, 
but each particle moves freely under the forces that are 
impressed, whether they act immediately upon it, or 
through the intervention of the adjacent particles. 

Fluids thus transmit any force applied to one of their 
surfaces equally in all directions; and if a fluid be in- 
closed in a vessel, and a force act upon any portion of its 
surface, as by means of a piston perforating one of the 
sides of the vessel that contains it, the pressure upon every 
remaining portion of the vessel will be equal, upon an 
equal surface, to that acting upon the piston : thus, if the 
piston be a square inch, and be acted upon by a force equiv- 
alent to a pound, every square inch of the surface of the 
vessel will also have to sustain a pressure equivalent to a 
pound. 

When a fluid is kept in equilibrio in an open vessel, by 
extraneous forces, these forces must act perpendicularly 
to the uncovered surface of the fluid, and if the fluid be 
acted upon by gravity, its surface must therefore be hori- 
zontal, or perpendicular to the direction of gravity. In a 
small vessel, the surface is a horizontal plane, inasmuch as 
the forces may be considered as acting in parallel lines, 
but in large masses of gravitating fluids, as the ocean or 
great lakes, the surface becomes parallel to the general 
figure of the earth. 



PRINCIPLES OF MECHANICS. 19 

Any line drawn upon such a surface, or parallel thereto, 
is called a level line, or more simply, a Level. 

When a gravitating fluid is placed in a bent tube, or in 
vessels communicating at bottom, it rises in the two branches 
of the tube, or in the several vessels to the same level. 
And if a pipe be inserted in a close vessel, the pressure on 
the sides of it will be proportioned to their surface, and the 
height of the fluid in the pipe. If the fluid in the pipe be 
acted upon by some extrinsic force, the action will be trans- 
mitted to the sides of the vessel, and the whole pressure upon 
them will be as much greater than the pressure upon the 
fluid in the tube, as the surface of the vessel is greater than 
the area of the tube. This principle has been applied to the 
construction of an instrument, in which a small force, acting 
through the intervention of a liquid, is made capable of ex- 
erting an intense pressure. It is called the water-press 
pump, or, after the name of the inventor, Bramah's press. 
The pressure of a gravitating fluid upon a horizontal base, 
is not proportioned, as in solid bodies, to the mass or 
weight of the fluid, but to the surface, and the height of the 
level surface of the fluid above the base. The measure of 
such pressure is the weight of a parallelopepid of the fluid, 
whose base is equal in area to the base of the vessel, and 
whose altitude is equal to the depth of the fluid. It is there- 
fore the same, whatever be the capacity orshape of the 
vessel, provided the area of the bottom, and the depth of 
the fluid remain constant. 

Upon surfaces that are not horizontal, the measure of 
the pressure of a gravitating fluid is the weight of a paral- 
lelopepid of the fluid, whose base is equal in area to the 
surface pressed, and whose altitude is equal to the depth of 
the centre of gravity of that surface beneath the level of 
the fluid. 

Although the pressure upon a given surface depends 



20 PRINCIPLES OF MECHANICS. 

upon the position of its centre of gravity, yet this is not the 
point to which the resultant of the hydrostatic pressure is 
applied. This last point is called the Centre of Pressure, 
and it coincides with the point which would be the centre of 
oscillation of the surface. Hence, in the calculations of the 
strength of the sides of vessels, or of walls to contain masses 
of fluids, the resultant of the resistances they oppose, must 
pass through this point, and be at least equal to the hydro- 
static pressure of the fluid. 

When a body is placed in a fluid whose weight is less 
than that of an equal bulk of the fluid, it rises and floats at 
the surface, and as much of it is immersed as displaces a 
mass of the fluid whose weight is equal to its own. 

In general, if any solid body be placed in a fluid, it will, 
if lighter, rise to the surface, if heavier, sink to the bottom, 
and the force with which it will rise or sink, will be equal 
to the difierence between its own weight and the weight of 
an equal bulk of the fluid. Hence, a body immersed in a 
fluid loses as much of its weight as is equal to the weight of 
a mass of fluid of equal bulk. 

Were the particles of fluids to move independently of 
each other, they would issue, from an orifice in the bottom 
or side of a vessel that contains them, with the velocity a 
falling body would acquire in descending from the surface 
of the fluid to the level of the orifice, and the section of 
the stream would be equal to the area of the orifice, and of 
the same size every where. But in consequence of the 
mutual action of the particles, the stream in passing through 
an orifice, cut in a thin plate, does not continue of the same 
area with the orifice ; it is at first contracted, and if the 
orifice be circular, the place of greatest contraction is at a 
distance from the vessel, equal to the radius of its orifice ; 
the shape of the jet is a truncated cone, whose greater base 
is equal to the area of the orifice, and whose least bears to 



PRINCIPLES OF MECHANICS. 21 

it the proportion of 5 : 8. An opening in a thick sided 
vessel discharges more, and pipes of different forms give 
greater or less increases to the above ratio. The quantity 
of water is measured by multiplying the velocity by the area 
of the less base of the truncated cone, which is called the 
'Vena Contracta. 

9. The comparative weight of equal bulks of different 
bodies is called their Density. We usually compare these, 
by means of a conventional standard, whose density forms 
the unit in which the densities of the rest are estimated. 
Densities thus estimated are called the Specific Gravities 
of the bodies, and the body employed as the standard in 
most cases is Water. 

In estimating specific gravities, it is not merely neces- 
sary that the water be pure, but, as both the bodies are 
capable of assuming different densities at different tem- 
peratures, it is necessary to define the temperature at which 
the experiments shall be made. The best temperature for 
this purpose is, for reasons we shall hereafter state, from 
38° to 40" of Fahrenheit's thermometer. To determine 
specific gravities, we make use of the principle that a body 
loses in water, as much weight as is equivalent to the weight 
of an equal bulk of water. If then a body be weighed in 
air, and afterwards in water, the difference is the weight of 
an equal bulk of water, and as water is the unit, we have 
only to divide the weight in air by the loss of weight, and 
the quotient is the specific gravity. 

The instrument by which specific gravities are thus de- 
termined, is called a hydrostatic balance. It differs from a 
common balance only in having a convenient apparatus 
added, by which the weight in water can be determined. 

It sometimes becomes necessary to determine the spe- 
cific gravity of bodies lighter than water. In this case the 



22 



PRINCIPLES OF MECHANICS. 



body, after being weighed in air, is attached to a body suffi- 
ciently heavy to cause it to sink, and whose weight in air, 
and weight in water are known. The dividend is, as before, 
the weight of the light body in air, the divisor is the differ- 
ence between the loss of weight of the heavy body, and the 
loss of weight of the two united. 

The Specific Gravities that are of most frequent use in 
the construction of steam engines, are as follows, viz. 

Table of Specific Gravities. 



Water at its maximum density 
Mercury, - - - - 
Lead, - - - - 
Copper, Cast, 

Rolled, 
Brass, Cast, 

Rolled, 
Iron, Cast, 

"Wrought, 
Steel, - Hard, 

Soft 
Tin, - - - - 
Zinc, _ - - - 

Sea Water, - - - 
Dry Oak, - - - - 
Yellow Pine, - - - 
White Pine, - - - 



1.000 
13.568 
11.352 

8.788 
8.878 
8.396 
8.544 
7.207 
7.788 
7.816 
7.833 
7.291 
7.190 
1.026 
0.932 
0.657 
0.569 



10. When two fluids of different densities press against 
each other in opposite branches of a bent tube, they will 
come to rest, in their respective branches, at heights, above 
the common level, inversely proportioned to their respec- 
tive densities. 

Upon this last stated principle, v/e may determine the 
pressure of the mass of elastic fluid which surrounds our 
Earth, and which is called the Atmosphere. If a piston be 
fitted air tight, in a glass tube about three feet in length. 



PRINCIPLES OF MECHANICS. 23 

and the lower end immersed in a vessel of mercury, the 
tube being held in a vertical position, and if the piston be 
drawn upwards, the mercury will follow the piston as it 
ascends in the tube, being forced up by the pressure of the 
atmosphere. When, however, the piston reaches a height 
of about thirty inches, the mercury will cease to follow, 
and an empty space will be left between its surface and 
the lower side of the piston. 

In like manner, if a tube, closed at one end, be filled 
with mercury, and being closed by the finger, inverted, and 
the open end plunged in a basin of mercury, the mercury 
will remain suspended in the tube, if its length be less than 
thirty inches ; but if it be longer, and the tube be held verti- 
cally, the mercury will descend, flowing into the basin until 
its surface stand at a level of about thirty inches above the 
surface of the mercury in the basin. 

This height of thirty inches is not constant, but varies in the 
same place, in consequence of changes which are constantly 
occurring in the pressure of the atmosphere ; it also varies 
in different places, in consequence of their being at differ- 
ent elevations above the level of the sea, and bearing, in 
consequence, columns of air of varying depths ; but at the 
level of the sea, the mean pressure is such as will support 
thirty inches of the mercury. 

Now acccording to the principle we have laid down, the 
pressure of this column of mercury upon a base of a square 
inch, will be equal to the weight of thirty cubic inches of 
mercury. This is almost exactly fifteen pounds, at which 
it is usual to estimate the pressure of the atmosphere upon 
every square inch of the surface of bodies subjected to it. 
This pressure, being that of a fluid, is equal in all directions, 
and hence is imperceptible to us, unless when it is taken 
off upon one part of a body, when that exerted on the 
opposite side becomes sensible. So far from tending to 



24 PRINCIPLES OF MECHANICS. 

crush bodies placed in it, the atmosphere rather acts to sup- 
port them, by bearing as much of their weight as is equal 
to the weight of an equal bulk of atmospheric air. 

11. If the sealed tube be not entirely filled with mercury, 
a portion of air remains in it ; when the finger is pressed 
on the open end and the tube inverted, the air rises to the 
closed end of the tube ; and when the apparatus is plunged 
in a basin of mercury, and the finger removed, the air within, 
being no longer compressed by the whole force of the 
atmosphere, will increase in bulk, and occupy a greater 
space than it originally filled, forcing out a part of the mer- 
cury. 

It is a law that holds good' in all elastic fluids, that they 
occupy spaces which are inversely as the pressures to 
which they are subjected and their densities are in conse- 
quence in the direct ratio of the pressures. Hence the 
difference between the height of the mercury in the tube 
that contains air, and that to which it rises in one void of ^ 
air, will be the measure of the density of the air thus con- 
tained, or of the pressure of any other elastic fluid, separat- 
ed by a column of mercury from the open atmosphere. 

The experiment, with a tube containing mercury, and in- 
verted in a basin of the same liquid, by which we measure 
the pressure of the atmosphere, was planned by Toricelli, 
and goes by his name. The apparatus, when attached to 
a support, and furnished with a scale on which the height 
of mercury in the tube can be measured, is called a Barom- 
eter. Of this there are several forms, and it is applicable 
to many important uses, of these, however, it is not our 
province to treat. 

The same force which is capable of raising a column of 
mercury thirty inches in height, is capable of raising a col- 
umn of water as much longer as the specific gravity of mer- 



PRINCIPLES OF MECHANICS. 35 

cury is greater than that of water. This height is about 
thirty-four feet. Hence, if by any means a vacuum be made 
in atube whose height is not greater than thirty-four feet, and 
its end be plunged in a mass of water, the fluid will rise and 
fill it. If the vacuum be imperfect the water will still rise, 
but to a less height. Such is the principle upon which the 
common pump acts, where a piston furnished with a valve 
opening upwards, and moving with reciprocating motion in 
a tube, also furnished with a valve opening upwards, ex- 
hausts a portion of air at each stroke, whose place is sup- 
plied by an equal quantity of water, until the water rises 
through the valve of the piston, and is lifted by it to the 
spout of the pump. Such also is the cause which supports 
a fluid in the branches of a syphon tube, whence it will 
flow with a force depending upon the difference in level, 
of the surface of the fluid in the vessel to which it is ap- 
plied, and the open end of the syphon. 

The TorricelUan apparatus may not only be made the 
measure of the pressure of the atmosphere, and of the 
elasticity of gaseous matter contained in its tube, but may 
be apphed to measure the pressure of any fluid immiscible 
with mercury, whether elastic or not. Neither is it neces- 
sary that its open end be immersed in a basin of mercury ; 
but if it be turned up like an inverted syphon, the fluid 
whose pressure is to be measured, will act upon its open 
end, and the measure of the pressure will be a column of 
mercury whose altitude is the diflerence of the level of 
that fluid in the two branches of the tube. 

If both ends of the bent tube be open, but while the one 
communicates with the atmosphere, the other is acted upon 
by a fluid contained in a close vessel, the diflerence of the 
two levels of the mercury will now be the measure of the 
excess or defect of the pressure of the confined fluid, above 
or below the pressure of the, atmosphere. 

4 



26 PHYSICAL PRINCIPLES. 

11. The great natural agent which, as we have said, acts 
in opposition to the attraction of aggregation, is Heat. Of 
its actual nature we know nothing, and it would be worse 
than useless to enter here into a consideration of the diffe- 
rent hypotheses that have been framed in respect to it. It 
is, however, capable of acting upon our senses, producing 
the sensation of warmth, and of exercising influences of 
various natures upon all bodies. By means of these actions 
which determine its properties, it may be studied, and the 
laws of its action ascertained. 

The first effect of heat of which we shall treat, is that of 
expanding the bodies submitted to its action. It is a gene- 
ral law, that all bodies increase in bulk when heated, and 
contract when cooled. But the manner and rate of their 
expansion and contraction differ, both w^ith the mechanical 
and individual nature of the substances. 

Of solids, each different species expands at a different 
rate ; but in all bodies of the same material, the expansion 
is equal for equal increments of temperature. 

In liquids, not only does each different liquid expand at 
a different rate, but the same liquid expands unequally for 
equal increments of heat at different temperatures. The 
expansion is least rapid when the temperature is not far 
from that at which the liquid congeals, and is most rapid as 
it approaches that at which the liquid boils. 

In elastic fluids, whether gases or vapours, not only is 
the expansion of each uniform for equal changes of tempe- 
rature, but the rate of expansion is identical in them all. 

12. We apply this property of heat to the construction 
of instruments for measuring its intensity ; such instru- 
ments are called Thermometers. They are now usually 
composed of a small tube, on the end of which a bulb is 
blown and in which a portion of Mercury is placed. The 



PHYSICAL PRINCIPLES. 27 

mercury is heated until it either fill the tube by its expan- 
sion, or, if the scale be intended to be long, with its vapour ; 
the end is then closed by heat. When the mercury cools, 
it shrinks in the tube and leaves the upper part free, and it 
will occupy a different space according to the temperature 
to which it is heated. To make such instruments capable 
of comparison with each other, it is necessary to adopt 
fixed points that may be easily obtained in all places. Of 
these, there must be at least two, and those which are now 
universally used, are what are usually called the Boiling 
and Freezing Points of water. 

It is, as we shall see hereafter, a well established fact, that 
the water which runs from melting ice is of the same tem- 
perature under all possible circumstances ; and that the 
heat of boiling water under equal atmospheric pressure is 
also constant. In the latter case, therefore, it is necessary 
to define the pressure at which the experiment shall be 
made, and this has been established by usage, at the mean 
pressure of the atmosphere at the level of the sea, or when 
the Barometer stands at 30 inches. 

The scale which is usually employed upon thermometers 
in this country and in England, is that of Fahrenheit. 
This has the number 32 opposite to that point in the 
stem of the instrument where the mercury stands in melt- 
ing ice ; this is called the freezing point. Between this 
and the point at which the mercury stands in water boiling, 
when the barometer has a height of thirty inches, the space 
on the stem of the instrument is divided into 180 equal 
parts. Opposite to the temperature of boiling water there- 
fore, the number 212% equal to 180o+32% is placed. The 
mark O*' is thirty-two divisions or degrees below the freez- 
ing point, and as mercury is capable of bearing, without 
congealing, even lower temperatures, and as they have 
actually been observed and may become the object of 



28 PHYSICAL PRINCIPLES. 

experiment, the scale is extended below this point as far 
as 40 equal divisions ; these are also called degrees, but to 
distinguish them from those above 0**, and to enable such 
temperatures to be made use of in calculation, the numbers 
are arranged in inverted order, and distinguished by the 
negative sign. 

To measure temperatures that are not greater than that 
at which mercury boils, the scale is carried upwards, also 
by equal degrees, to about 600°. Mercury boils at 575", 
and freezes at — 40% and thus the whole scale of Fahrenheit 
includes 615 equal divisions or degrees. 

Mercury, like other fluids, is subject to the law of a 
diminished expansion near the point of its own congelation, 
and one increased near the temperature of its boiling ; 
hence the equal divisions on the scale do not correspond 
exactly with equal increments of temperature. But as the 
rate of expansion is very nearly uniform at all mean 
temperatures, at which by far the greater portion of 
philosophical inquiries are made, no practical error of any 
importance can arise, from considering the degrees of the 
thermometric scale as corresponding to equal changes of 
heat. 

13. Furnished with such a measure of heat, experiments 
may be made upon the expansion of the several classes of 
bodies. The results of such of these as are most impor- 
tant in reference to our subject are given below, viz. 



PHYSICAL PRINCIPLES. 29 

Lineal dilatation of some of the metals for each degree of 
Fahrenheit's thermometor, expressed in decimals of their 

length at the temperature of Melting Ice. 



J 

Copper, ----- 


0.0000096 


Brass, - _ - - - 


0.0000104 


Wrought Iron, - - - - 


0.0000068 


Cast Iron, - - - - - 


0.0000061 


Soft Steel, 


0.0000059 


Tempered Steel, - - - 


0.0000069 


Lead, ------ 


0.0000158 


Tin, 


0.0000121 

1 



The cubical expansion of these bodies can be deduced 
from the above table, for it is a fact that is confirmed both 
by theory and experiment, that the fraction, which repre- 
sents the expansion of any body in bulk, is just three times 
as great as that which represents its lineal expansion ; the 
solid contents being taken as unity in the first case, and the 
length in the second. 

The whole dilation of Water between its boiling and 

points, is Y2 

Of Alcohol, h 

Of Mercury, " " - - " - jV 
Within these limits the expansion of Mercury is tolerably 
uniform, indeed if contained in a glass tube, the joint 
effect of the expansabilities of the two bodies is to produce 
absolute uniformity, but water is not only liable to unequal 
rates of expansion at varying temperatures, but is also sub- 
ject to a remarkable anomaly. When water is taken as it 
flows from melting ice, so far from expanding by the first 
application of heat, it contracts. This contraction con- 
tinues until it reaches the temperature of 38% from this 
point until it be heated to 40 '^ its bulk undergoes no per- 
ceptible change ; heated beyond 40'' it begins to expand, 



30 PHYSICAL PRINCIPLES. 

and continues to do so in an increasing ratio until it begins 
to boil. Hence water is at its maximum of density at a 
temperature of from 38 "^ to 40% and this being a physical 
state that can be defined independent of the thermometer, 
it is then best suited to be used as the unit in determining 
specific gravities. 

The densities of water at various temperatures are as 
follows, viz. 



1 






1 


32° 


.99989 


79° 


.99682 


34° 


.99995 


100° 


.99299 


39° 


1.00000 


122° 


.99753 


44° 


.99995 


142° 


.98182 


49° 


.99978 


162° 


.97552 


J 54° 


.99952 


182° 


.96891 


59° 


.99916 


202° 


.96198 


69° 


.99814 


212° 


.95860 


-- - - ,._ 









When water congeals it suddenly expands, increasing in 
bulk one-ninth part of its former dimensions. By this 
sudden dilatation it becomes capable of producing the most 
powerful mechanical effects. Other substances also ex- 
pand suddenly on passing from a fluid to a solid state ; 
among these is cast iron, and this expansion is among the 
most important of the practical difficulties that attend the 
making of the parts of steam engines. 

We have stated that all elastic fluids, not only expand 
uniformly, but that the rate of expansion is the same in all. 
By the experiments of Dalton and of Guy Lussac, this 
dilatation is found to be 0.375 of the bulk, between the 
temperatures of freezing and boiling water, or 0.00208 
for every degree of Fahrenheit's thermometer. 

14. When bodies are exposed to the action of heat, 
even when it is not sufficiently intense to produce any 



PHYSICAL PRINCIPLES. 31 

change in their mechanical state, they are found to be un- 
equally affected in temperature by equal intensities of heat. 
Thus, for instance, the heat necessary to raise the tempe- 
rature of a pound of water 3 ° , will be sufficient to heat an 
equal weight of mercury 100°. The heat thus absorbed 
by different bodies, in raising equal weights an equal num- 
ber of degrees is called their Specific heat. We know 
nothing of its absolute quantity, and are therefore compel- 
led to express merely the ratio between the specific heats 
of the different substances, and this is usually done by 
taking the specific heat of water as unity. 

Specific Heat of different bodies between the temperatures of 
Boiling and Freezing Water, according to Messrs, Petit 
and Dulong. 



Water, 
Mercury, - 
Platina, 
Copper, - 
Iron, - 

Atmospheric Air, 
Hydrogen, - 
Oxygen, - 
Steam, 



1.0000 
0.0330 
0.0335 
0.0940 
0.1098 
0.2669 
3.2936 
0.2361 
0.8470 



All bodies when compelled to change their volume have 
their capacities for specific heat affected. When they are 
condensed their capacity is diminished, when they expand 
their capacity is increased. Hence, in the former case 
their temperature is elevated, in the latter it is lowered. 
In solid bodies that are not elastic, percussion and pressure 
heat them, and in some cases until they are red hot. The 
heat evolved at first is the greatest, and they finally when 
the density becomes the greatest that the pressure can 



32 PHYSICAL PRINCIPLES. 

produce, cease to be further heated. In liquids the small 
increase of temperature that is caused by pressure, is 
exactly compensated when the pressure is removed. 
Gases and vapours are also affected in a similar manner, 
w^hen they are condensed their temperature is raised, 
when they expand it is lowered. Steam is also subject to 
the same law, and thus when allowed to escape from a 
vessel in which it is generated under pressure, it rapidly 
assumes, in expanding, the temperature that belongs to 
steam, generated under the lessened pressure to which it 
is now exposed. 

15. When ice at a temperature below 32*' is exposed to 
the action of heat, its temperature is readily raised to that 
degree ; here the elevation of temperature suddenly ceases, 
the ice begins to melt, and no farther increase of tempera- 
ture can be attained, until the whole of the ice be melted. 
It is hence inferred that a portion of the heat applied, and 
which becomes insensible, is necessary to the constitution 
of the liquid, and resides in it in a state we call Latent. 

In the same manner, the water proceeding from melting 
ice begins to shew an increasing temperature as soon as 
the whole of the ice is melted -^ the temperature continues 
to increase until it be raised to 212% at this point the liquid 
begins to boil, or throw off steam rapidly, but the tempera- 
ture of the water cannot be increased any longer. The 
steam that rises from the water has a similar temperature 
with the boiling liquid, and we infer from these two facts, 
that heat also passes into the latent state, when it converts 
water into steam. When the steam returns to the state of 
water, and water passes into the state of ice, the heat that 
became latent in the previous change, is again given out, 
and becomes sensible. To distinguish between sensible 
heat and that which is specific or latent we employ, to de- 



PHYSICAL PRINCIPLES. 33 

signate the former, the term Temperature, a word we have 
hitherto been compelled to make use of without ex- 
plaining it. 

The quantity of sensible heat which becomes latent on 
the liquefaction of ice is about 135" of Fahrenheit. 

The quantity of sensible heat which becomes latent when 
water passes to the state of steam under the mean pressure 
of the atmosphere, is 990". 

But water, as we shall see, is capable of forming vapour 
at all temperatures. It is found, that in every case, the 
sum of the sensible and latent heat is a constant quantity, 
or is equal to 1102°. 

All other cases of liquefaction and evaporation are attend- 
ed with similar phenomena of latent heat ; and it is a 
general law that whenever a body changes its mechanical 
state its relations to temperature are also changed. 

16. When the surface of a liquid is exposed, either at 
ordinary temperature, or submitted to the action of 
heat, it is gradually dissipated. The same dissipation takes 
place in a greater degree, when the pressure of the atmos- 
phere is lessened or removed altogether. At some par- 
ticular temperature, under the mean pressure of the atmos- 
phere, Hquids throw off vapours with great rapidity, and 
the process which is attended with a violent agitation, is 
called ebullition. If the pressure be lessened, ebullition 
takes place at a lower temperature, until in the vacuum of 
an air-pump, water will boil at about the heat of the blood. 
When the liquid is heated in a close vessel it may be raised, 
under an increased pressure, to a temperature far above that 
at which it boils in the open air. The steam generated 
in all these cases, has the same temperature as the liquid 
■jvhence it flows, and contains besides heat in a latent state, 
according to the law we have just stated. The expansive 

5 



34 



PHYSICAL PRINCIPLES. 



force of steam, at various temperatures, is very different. 
At 212° it just exceeds the pressure of the atmosphere, 
and hence becomes capable of escaping from an open 
vessel, in quantities just sufficient to carry off, in a latent 
state, all the heat that is communicated to the liquid, which, 
when it has once reached this temperature, does not grow 
warmer until the whole be evaporated. The general law 
of the tension or expansive force of aqueous vapour is, that 
while the heat increases in arithmetic progression, the ex- 
pansive energy increases in a geometric ratio. Its pressure 
doubles for every 40° of Fahrenheit, as will be seen to be 
nearly true from the following table. 

Table of the Elastic Force of Steam. 













I 


Temperature. 


Pressure in 
Atmosphere. 


Pressure per 
Sq. in. in Ihs. 


Temperature. 


Pressure in 
Atmosphere. 


Pressure per 
Sq. in. in lbs. 


212" 


1 


15 


365° 


14 


210 


251° 


2 


30 


369" 


15 


225 


275° 


3 


45 


372° 


16 


240 


291° 


4 


60 


375° 


17 


255 


304° 


5 


75 


378° 


18 


270 


315° 


6 


90 


381° 


19 


285 


324° 


7 


105 


384° 


20 


300 


331° 


8 


120 


387° 


21 


315 


338" 


9 


135 


390° 


22 


330 


345° 


10 


150 


392° 


23 


345 


351° 


11 


165 


394° 


24 


360 


356° 


12 


180 


396° 


25 


375 


361° 


13 


195 


398° 


26 


390 












1 



To find the force with which steam tends to burst the 
vessels in which it is generated or confined, 151bs. must be 
deducted from the numbers in the third column of the 
above table, inasmuch as the pressure of the atmosphere 
acts in opposition to the elastic force of the steam. 

The density and volume of steam at different tempera- 
tures may be ascertained by means of the following table 
in which the density and volume of steam, estimated in re- 



PHYSICAL PRINCIPLES. 



35 



iation to water, taken as the unit, are given for elastic forces 
estimated in atmospheres. 

Table of the Density of Steam under Different Pressures. 



r 




il 


Pressure in 
Atmospheres. 


Density. 


Volume. 


1 


0.00059 


1696 


2 


0.00110 


909 


3 


0.00160 


625 r 


4 


0.00210 


476 


5 


0.00258 


387 


6 


O.OO306 


326 


8 


0.00399 


250 


10 


0.00492 


203 


12 


0.00581 


172 


14 


0.00670 


149 


16 


0.00760 


131 


18 


0.00849 


117 


20 


0.00937 


106 


L , . 




J 



When water or any other liquid is subjected to the action 
of heat in a close vessel, it rapidly attains its boiling tempe- 
rature ; the vapour thus thrown off adds to the pressure of 
the enclosed atmosphere and retards the boiling. The 
temperature of the liquid will then rise beyond the tempe- 
rature, at which it boils in the open air, until it reach a 
limit which varies in each different liquid. At this last 
temperature the whole mass of fluid is at once transformed 
into vapours of a great density, which fill the whole of 
the vase. 

As the elastic force of the vapour, which is formed in 
a close vessel, increases with great rapidity with the eleva- 
tion of temperature, it follows, that the vessels, in which 
liquids are thus enclosed to the action of heat, ought to be 
very strong, and capable of resisting a powerful pressure. 
But whatever be their strength, if there were no limit to 
the temperature of the liquid, the time must arrive when 



36 PHYSICAL PRINCIPLES, 

the expansive force of the vapour vrould exceed the cohe» 
sion of the vessel, and burst it into pieces with great 
violence. 

The means that may be resorted to, to limit the tempera- 
ture of a liquid enclosed in a close vessel, will be consider- 
ed when the structure of the boilers is treated of. 

We have just stated, that when a liquid was heated in a 
close vessel, the atmosphere of vapour formed within it, 
would retard the ebullition until a certain period when the 
whole liquid mass would assume the form of vapour. This 
remarkable fact was discovered by Cagniard de la Tour. 
His experiments give the following results. (I.) Ether is 
wholly converted into vapour in a close vessel, at a tempe- 
rature of 302% in a space less than twice its original bulk, 
and exerts an expansive force equal to 70 atmospheres. 
(2.) Sulphuret of Carbon is wholly converted into vapour 
at a temperature of 420% and has an expansive force of 

37 atmospheres. (3.) Alcohol and water have exhibited 
similar phenomena ; the exact circumstances under which 
they change their state have not been observed, but it has 
been found that alcohol, becoming vapour of three times 
its liquid bulk, exerted a force of 119 atmospheres; and 
that water, at a temperature about that at which zinc melts, 
expands at once into vapour of about four times its original 
bulk, exerting so great a force, that the experiment has 
been but seldom successful, in consequence of the breaking 
of the vessels in which it has been attempted to perform it. 

17. Heat is conveyed in various manners : It may pro- 
ceed directly from a heated body to those which surround 
it ; it may be conveyed through intervening bodies, or from 
one part of a body to another ; and in fluids it is distributed 
throughout the whole mass, by the motion itself generates 
among their particles. 



PHYSICAL PRINCIPLES. 37 

When a body at any temperature whatsoever is surround- 
ed by air, or plunged in a fluid, of a temperature lower than 
its own, it grows cooler, and finally assumes exactly the 
temperature of the medium in which it is placed. In all 
cases, a body hotter than those which surround it gives out 
to them its excess of heat, until an equilibrium of tempera- 
ture take place. 

When a body is placed in a vacuum, it still gives out its 
heat to the bodies which exclude the air, and finally, as 
before, comes to the same temperature with them. It is 
thus evident, that the heat possessed by a body, even when 
isolated in an empty space, passes through that space to 
the surrounding bodies. This heat, which is thrown off 
from every point of a heated body, is said to Radiate. 

Heat radiates not only when the body is placed in vacuo, 
but when it is surrounded by air, by other gases, and by 
liquids. And it is sufi&cient for the present purpose to 
examine how the radiation is performed in air, for not only 
are the experiments more easy than in a vacuum, but it is 
in this medium that radiation takes place most frequently. 
Air may diminish the intensity of the radiating heat, but 
does not alter the laws which it follows. 

Heat is thrown off by a heated body in right lined direc- 
tions, as if it issued from the centre of a sphere in the 
direction of its radii. When thus radiating, it is capable of 
being reflected ; and this reflection takes place in the same 
manner as that of light ; that is to say, the angle of Reflection 
is equal to the angle of Incidence, and both are included in 
a plane perpendicular to the reflecting surface. Polished 
surfaces reflect heat best, and it has been found to be a 
general law that the power both of absorbing and emitting 
heat from the surface of bodies, follows a common law, and 
is inversely proportioned to the power of reflection. The 
power of giving out heat is called that of radiating, and the 



38 PHYSICAL PRINCIPLES^ 

experiments which have been made upon this property in 
bodies give the following proportional results. 

Table of the Radiating Power of different Bodies. 



Lamp Black, 

Water, 

Writing paper, 

Glass, 

India Ink. 

Ice, 

Mercury, 

BriUiant Lead, 

Polished Iron, 

Tin, Silver, Copper. 



100 
100 

98 
93 
88 
85 
29 
19 
15 
12 



Of all substances examined lamp black and water ra- 
diate best, and polished metals worst. When a metal is 
scratched or tarnished, or when it is covered with a coat of 
water, of varnish, or even of woollen stuff, its power of 
radiation is increased. 

The inverse relation which takes place between the 
powers of reflection and absorption, might be almost in- 
ferred without the aid of experiment ; for all the heat 
which falls upon a surface must be either reflected or ab- 
sorbed, the less therefore that is reflected the more ought 
to be absorbed. The relation between the properties of 
radiation and reflection is not so obvious, but experiment 
shows that as the one increases the other diminishes. 

18. When the temperature of a body difters from that of 
the surrounding medium, its mode of heating or cooling 
depends not only on its power of radiating, absorbing, and 
reflecting heat, but also upon the manner in which the 
heat it receives or parts with, is distributed or withdrawn 
from its mass. No body permits radiating heat to penetrate 



PHYSICAL PRINCIPLES. 39 

to any great depth within its mass ; in solid bodies any 
farther heating is due to the radiation among their particles. 
This propagation of heat among the particles of bodies is 
called their conducting power. Different bodies possess 
this property in very different degrees : thus, a rod of glass 
may be safely held close to the place where it is in actual 
fusion, and a piece of charcoal, to the place where it is 
burning ; while if a bar of iron be heated red hot at one 
end, the other is so much heated that it cannot be safely 
touched. 

Gold and silver are the best of all conductors, and all 
the metals are good conductors ; clay and pottery are 
much worse, and charcoal still more so. Straw, wool, 
cotton, down, and other substances of similar structure, 
are the worst conductors among solid bodies. This is, 
however, in a great measure owing to the presence of air, 
which they confine in such a manner as to prevent its en- 
tering into circulation. Among the solid substances on 
which experiments have been made, the following relative 
powers of conducting heat have been observed. 



Table of the Conducting Power of different 


bodies. 


""- .1 


Gold, 


1000 


Silver, ------ 


973 


Copper, ------ 


&98 


Iron, ------ 


374 


Zinc, ------ 


363 


Tin, 


304 


Lead, ------ 


180 


Marble, 


24 


Porcelain, _ - - - - 


12 


Fire Brick, _ _ _ . - 


11 


II 



40 PHYSICAL PRINCIPLES. 

19. Liquids are in general worse conductors than any 
solid bodies. Their temperatures are, notwithstanding, 
rapidly raised by a proper application of heat. Thus, if a 
heated body be plunged in a liquid, the layers of the liquid 
immediately in contact with the body are heated ; they ex- 
pand, and become specifically lighter than those which 
surround them ; they in consequence rise, and are re- 
placed by others, which rise in their turn, and the motion 
continues, until the solid and the whole mass of liquid as- 
sume a common temperature. When the vessel that con- 
tains a liquid is heated from beneath, a double set of cur- 
rents is formed, one of the warmed particles which rise, and 
the other of cold which descend to supply the place of the 
former. But if the heat be applied to the top of the fluid, 
no more than the upper surface is heated, and the rest re- 
tains its original temperature, or is warmed in a degree 
hardly perceptible. 

20. Gases are affected in the same manner, but being 
less dense, they carry off, by their motions, less heat than 
liquids do ; and the radiation, which is hardly perceptible 
in a liquid body, becomes the most prominent cause of the 
cooling of a body exposed to the air. 

The rate of the cooling of a body, surrounded by a fluid 
medium, depends then, as well upon its power of radiation, 
as upon the abstraction of heat by the motion of the parti- 
cles of the medium. The quantity of radiation decreases 
in a geometric ratio as the temperatures are lessened in 
arithmetic proportion, and it depends upon the nature of 
the surface of the body. The rate of cooling by the con- 
tact of a fluid is, on the other hand, independent of the 
nature of the surface. Both the temperatures and the rate 
of cooling vary in geometric ratio, but the common multi- 



PHYSICAL PRINCIPLES. 41 

plier differs in the two progressions. In the temperatures 
it is 2, while in the rates of cooling it is 2.35. 

The cooling property of gases may always be expressed 
in terms of some power of their pressure. The coefficient 
of the power is, in air 0,45, in hydrogen 0.315, in carbonic 
acid 0.517. 

These laws are directly applicable to masses of fluid 
bodies, because heat or its diminution, is propagated in 
them with extreme rapidity by means of their internal mo- 
tion. In solid bodies the communication of heat is more 
slow : but in both, the laws both of heating and cooling are 
identical. 

21. When a solid body is cooled, by being placed in a 
medium whose temperature remains constant, the outer 
part cools first, and the temperature increases from the 
surface to the centre ; but this difference gradually be- 
comes less and less, and the whole will finally reach an 
uniform heat equal to that of the surrounding medium. 

When a solid body is placed in a medium of higher tem- 
perature than its own, the temperature will be at first great- 
est at the surface, and least in the centre ; but^ the heat 
will gradually penetrate, until the whole of the particles 
attain the heat of the surrounding mediums. 

When the solid is only heated at some one point of its 
surface, the remainder will receive heat by virtue of the 
conducting power. But, as every point in the surface will 
radiate heat, it becomes obvious that a limit will be reached, 
when the quantity of heat lost by radiation will be exactly 
equal to that communicated to the body. Thus the tempe- 
rature will become constant, but each different point will 
have that which will depend upon its distance from the 
point to which the heat is directly applied. 

6 



42 PHYSICAL PRINCIPLES. 

If a solid body be formed into a vessel, and contain a 
liquid, and if heat be applied beneath, the motion of the 
liquid will bring all the parts, with which it is in contact, 
to its own temperature, which the interi-or of the vessel 
will not surpass. The outside of the vessel will have a 
temperature as much greater as is due to its conducting 
power, and in metallic vessels, the difference will be hardly 
perceptible. But if the heat be applied above the surface 
of the liquid, the latter will no longer act to prevent this 
part of the vessel being heated as high as the substance that 
furnishes the heat is capable of doing. So also, if the heat 
be applied below the surface, but near it, little or none of 
the heat will descend through the solid sides of the vessel. 

If, by any accident, a non-conducting substance be in- 
terposed between the vessel and the liquid, in this case also> 
the vessel may acquire a heat greater than that of the liquid, 
and the heat will be distributed as if no liquid were presents 



CHAPTER II. 



COMBUSTION. 



Definition of Combustion, — Oxygen. — Flame,- — Atmospheric 
Air. — Currents of Air produced by Combustion, — Increase 
of Weight in the process of Combustion. — Temperature of 
Flame, and modes of burning of Solids, Gases, and Li' 
quids. — Different species of Fuel. — Properties and Chemi- 
cal J^ature of Fuel. — Carbon and Hydrogen. — Compara- 
tive value of different kinds of Fuel. — Parts of Furnaces. — 
Ashpit. — Grate. — Body of the Furnace. — Flues, — Chim- 
neys. — Damper, — Furnace Doors, 

22. Of the various sources of heat, but one is of impor- 
tance in its relation to our subject, this is the chemical 
process which is called Combustion. This process, in its 
general and most extended sense, denotes the combination of 
bodies with a class of simple substances, that are thence 
called Supporters of Combustion ; as applicable to our 
present object, it is restricted to their combinations with but 
one of them, namely, Oxygen. 

23. Oxygen is an insipid, colourless, ponderable body, 
which we find existing in nature in a gaseous state, and which 
possesses the property of entering into combination with 
all well known simple substances, with a greater or less 
degree of energy. These combinations are all attended 
with the developement of a greater or less degree of heat, 



44 COMBUSTION* 

and the quantity of heat appears to he proportioned to tW 
energy of the action by which the combination is effected* 

24. It is a general law, that all bodies when intensely 
heated become luminous. When this heat is produced by 
combination with oxygen, they are said to be ignitedj and 
when the body heated by this chemical action is in a gas* 
eous state, it forms what is called Flame. 

25. Oxygen is one of the principal constituent parts of 
atmospheric air, of which it forms about one-fifth part, 
and it is from the atmosphere that the oxygen which is 
the agent in the combustions, that we apply to generate 
artificial heat, is derived* Although it is thus absorbed 
from the atmosphere in large quantities, by processes both 
natural and artificial, it does not suffer diminution in quan* 
tity, for there are several natural actions that are constantly- 
restoring and replacing it. By a peculiar mechanical lavsr 
that affects elastic bodies, they are uniformly distributed 
over the surface of the earth, each acting as if it were a 
distinct atmosphere, and hence the quantity of oxygen 
in the air is identical in all places, and under all circum- 
stances. 

Not only is the quantity of heat developed by the com>* 
bination of different bodies with oxygen extremely variable, 
but that at which they begin to combine is also very differ- 
ent. There are some that unite with it at the ordinary 
temperature of the atmosphere, while others require to be 
previously subjected to the most intense heat we have the 
means of producing ; there are others again, with which it 
will only combine at the moment in which it is in the act 
of being separated from some of its other chemical com* 
binations* 



COMBUSTION. 45 

^6. As the oxygen forms, in the process of comhustion, 
a combination with the combustible body, it is obvious that 
a given quantity of atmospheric air, must have its property 
of supporting combustion rapidly destroyed, and hence 
whenever the process is intended to be continued, it is 
necessary to supply constantly fresh masses of air. The 
very process itself is, however, capable of creating cur- 
rents in the atmosphere, that will continue until a great 
part or the whole of the combustible has entered into com- 
bination ; and we may, by a skilful application of mechani- 
cal principles, regulate and govern the supply of air thus 
drawn towards the burning body. In some cases, however, 
where intense heat is desired, it becomes necessary to 
urge, over the surface, or through the mass of the com- 
bustible, currents of air by mechanical means. Apparatus 
for this purpose are called Blowing Machines, of which the 
common bellows is the most familiar instance. 

The currents that we have spoken of are formed upon the 
principle, by which, as we stated in the last chapter, bodies 
are cooled when placed in fluids. The oxygen generally en- 
ters into combination with most of our common fuel, without 
losing its gaseous form, and although more dense at a given 
temperature than it was before, it is generally so much 
heated as to become specifically lighter than the adjacent 
air, while the rest of the mass of air becomes equally heat- 
ed, without undergoing any chemical change ; it therefore 
rises along with the oxygen that has entered into combina- 
nation, and the contiguous air rushes towards the burning 
body, in order to supply the place of the rising column. 
Chimneys or flues are usually adapted to carry up the 
heated air. The draught of these is rendered more intense, 
by permitting no air to enter them, but what passes through 
the fuel ; and the quantity that shall thus pass may be regu- 
lated, either by changing the magnitude of the opening by 



46 COMBUSTION. 

which the air enters the fire, or by varying the area of the 
flue. An apparatus intended to fulfil the former of these 
objects is called a Register, one to fulfil the latter, a 
Damper. 

27. Although the density of oxygen is by no means great, 
still as it is ponderable, it must in all cases increase the 
weight of the combustible. This, at first sight, appears 
contrary to ordinary experience, which perceives bodies 
wasting and diminishing under the process of combustion. 
This apparent anomaly grows out of the fact, that the pro- 
ducts of the process are in many cases gaseous, and hence 
escape along with the current of air that passes through the 
burning body. Were we to collect the whole of the products, 
we should find in them an increase of weight, exactly equal 
to that of the oxygen which has been consumed. 

28. Different bodies become luminous in the process of 
combustion, at different temperatures, solids more early 
than gaseous bodies. None appear to become visible, even 
in a faint light, below a temperature of about 870° of Fah- 
renheit. The light is at first of a dull red colour, as the tem- 
perature augments the light becomes more brilliant, and the 
body finally shines with an intense white light. Solid bodies 
may become luminous when heat is simply communicated to 
them, and without entering into combustion, but gases are 
never luminous except while entering into combination. 
Liquids burn only by becoming volatile, and hence it is the 
aeriform matter that escapes, and not the liquid itself that 
becomes luminous. 

When a combustible is solid, and so fixed as not to be- 
come volatile by the heat generated by its own combustion, 
it burns only at the surface, and the heat generated resides 
in the place where the combustion occurs, whence it is 



COMBUSTION. 47 

propagated to the surrounding bodies by radiation or by 
their conducting power, except so much as is applied to 
heat the current of air that flows through the mass of burn- 
ing fuel. But if the body be one that is capable of becom- 
ing gaseous at a temperature below that at which it ignites, 
the combustion takes place principally in the gaseous mat- 
ter, extends into the column of rising air, and into the flue 
by which it is conveyed. The heat the vapours acquire in 
their combination with oxygen renders them luminous, and 
it is far more intense than that found where the fuel is 
itself situated. SoUds may become volatile either by the 
physical process of evaporation, or by their constituents 
entering into new combinations, whose natural state is that 
of gas ; Flame is the product of their combination with 
oxygen in either case. 

The briUiancy of a flame is no criterion of the intensity 
of its heat. The flame of the compound blowpipe, the 
most intense in heat of any that we can produce, is barely 
visible in the open day. Those flames are most brilliant, 
in which a gas is concerned, that has a constituent capable 
of returning to the solid form during the process ; this 
being capable of becoming more luminous at equal tempe- 
ratures than gas, imparts this property to the flame of 
which it constitutes a part ; such is the cause of the intense 
brilliancy of the flame of carbonated hydrogen, in the form 
of oil and coal gas, or of its purer state, obefiant gas. 
Flame may be cooled until the gas ceases to be luminous, 
or to unite with oxygen. This is done by bringing into 
contact with it a metallic body, or other good conductor ; 
in this case no fresh heat is generated in the current, which 
therefore no longer produces any new calorific eflect. 

Flame, as a general rule, is hollow ; that is to say, the 
gaseous matter combines with oxygen only at its surface, 
except under particular circumstances : thus when an in- 



48 COMBUSTION. 

flammable gas is intimately mixed with oxygen, the whole 
inflames suddenly and explodes, and when currents of air 
are propelled violently into the body of the flame the heat 
is more intense, and less of the fuel escapes unconsumed 
than in cases of ordinary draught ; the whole gaseous mat- 
ter too, may be consumed within a less space. This prin- 
ciple has been advantageously applied in this country to 
the boilers of several steam engines, where as the space is 
limited, a more complete combustion within it is discernable. 
For this purpose a fan wheel has been used and with 
great advantage. A similar plan has been more recently 
introduced in England, in the boiler of a locomotive engine, 
which will be hereafter spoken of. 

The current of air which flows towards and through a 
a mass of burning fuel, produces two eflects, directly con- 
trary to each other. While on the one hand the oxygen, 
that is necessary for supporting the combustion, generates 
heat by entering into combination with the fuel, on the 
other, the residue of the atmospheric air, which constitutes 
four-fifths of the whole, carries off* a part, greater or less, 
of the heat thus produced. The actual effect in heating 
depends upon the diff'erence of these two effects, and is in- 
fluenced by the relation between the mass of air and that 
of the combustible. When the area of the current of air is 
small, when compared with the bulk of the combustible, as 
when it is directed through a tube of small diameter, the 
energy of the combustion is increased, and the flame is 
longer ; on the contrary, when the same quantity of air 
enters by a larger orifice, the flame diminishes in bulk, and 
may even be extinguished by the second of the above de- 
scribed actions. 

Although a body that- continues solid during combus- 
tion, burns only at the surface, the heat generated may be 
sufficiently intense to render the body luminous throughout; 



COMBUSTION. 49 

on the other hand, it is only at the surface that the currents 
of heated gas that constitute flame become luminous, but the 
solid matter conveyed by, or in the act of deposition from, 
such a current, will be luminous whether at the surface 
or not. 

Such are the general principles of combustion, and such 
the nature of flame ; they cannot be more fully developed 
except by considering the peculiar nature and mode of 
burning of the several species of fuel in actual use. 

29. Of the difl'erent species of fuel, those which are 
most commonly employed in generating steam are ; 

1. Pine Wood, 

2. Hard Wood, 

3. Bituminous Coal, 

4. Anthracite Coal. 

Each of these has its peculiar manner of burning, and 
hence the furnaces or fire-places in which they are used 
must differ in form and arrangement, as ought the flues 
and chimneys by which the current of air that passes through 
them is carried off". 

30. The general properties of a good fuel are, that it 
should burn easily in atmospheric air, and that the heat 
generated by the combustion should be sufiicient to keep 
it up, until the whole is consumed. The heat is carried ofl" 
from the fuel in three ways. 

1 . By the current of heated air. 

2. By the direct radiation of its solid part; and, 

3. By the radiation of the flame that issues, and the 
conducting power of the flues with which the flame comes 
into contact. In the application to the generation of steam, 
the first can be made but little use of, inasmuch as to cool 
this rising column of air would diminish its velocity, and thus 
lessen the draught of the chimney ; but both the kinds of 

7 



50 COMBUSTION. 

radiation, as well as the action of conductors on the flame 
should be employed, and the vertical part of the chimney, 
should not commence except at the distance from the 
mass of fuel, at which the flame terminates. The simple 
combustibles which are found in the four different kinds of 
fuel which we have spoken of, are Carbon and Hydrogen, 
the coals contain sulphur, but it is not, generally speaking, 
in sufficient quantity to aff'ect the manner of their combus- 
tion. There is also present a portion of oxygen. 

31. Carbon is a substance which exists in a state nearly 
^ure in common charcoal, and in the black deposit which 
is formed on the flues, through which the column of air 
that has passed through burning fuel is carried. 

In these forms it is a solid body of a deep black colour, 
insipid, and inodorous ; it is infusible by heat, and does not 
become volatile, but in most species of fuel it is, during 
combustion, divided into such small portions as to be readily 
carried off" by the heated air, and is then deposited upon 
the flues, forming, with other condensed matter. Soot. 

It combines with oxygen in two different proportions 
forming carbonic oxide, and carbonic acid. The former 
still retains the property of combining with oxygen, and, as 
it is gaseous, forms flame, which has a pale blue colour ; the 
latter is incombustible and extinguishes flame. 

Hydrogen, in its pure form, exists in a gaseous state, and 
is the lightest of all known substances, having a density of 
no more than one -fourteenth part of that of common 
atmospheric air. It combines with half its bulk, or eight 
times its weight of oxygen, when inflamed, and the com- 
pound that results is water, which, in consequence of the 
high heat generated by the combustion, is at first in a state 
of vapour. This combination is attended with the highest 
degree of heat we can obtain by any combustion whatso- 



COMBUSTION. 51 

ever, as is manifest from the effects of the compound blow 
pipe, in which an united stream of oxygen and hydrogen, 
in the proportions that constitute water are inflamed. 

Hydrogen also unites with carbon, forming one well 
known and universally admitted gaseous compound Olefiant 
Gas. It is found also in the gaseous shape containing a 
less proportion of carbon, but it is yet in dispute, whether 
any of the various gases of this character be definite com- 
pounds, or simply mechanical mixtures of olefiant gas with 
uncombined hydrogen. 

When a body, whether solid or liquid, that contains a 
combination of carbon and hydrogen, is exposed to a high 
heat, these gases are let loose and take fire ; other com- 
pounds, of which these two substances constitute an impor- 
tant part are also sometimes generated, but which are not 
combustible. 

Thus, not only does a part of the fuel burn in the body of 
the furnace or fire-place, and its more volatile part separate, 
but new combinations take place there, a part of which are 
also inflammable, and burn in the chimney, if a sufficient 
quantity of uncombined oxygen enter it along with them. 
These new inflammable products are carbonic oxide, and 
the carburetted hydrogens. 

32. Carbon, in burning, combines with no more than two 
and two-thirds of its weight of oxygen. In its combustion, 
one pound produces sufficient heat to increase the tempera- 
ture of 13000 lbs. of water 1" Fahrenheit. 

Hydrogen combines with eight times its weight of oxygen, 
and one pound of it, in burning, raises the heat of 42000 lbs. 
of water 1". 

Hence it is obvious, that of equal weights of fuel, that 
which contains most hydrogen, ought in its combustion to 
produce the greatest quantity of heat. Such, in truth, is 



52 



COMBUSTION* 



the case, where the fuel is exposed, each kind under the 
most advantageous circumstances. And thus in steam 
engines pine wood is preferred to hard, and bituminous 
coal to anthracite. But as hydrogen, and the new com- 
pounds it forms are easily separated in the form of gas, 
which also carries with it a dense smoke composed of 
minutely divided carbon, it is only when the whole smoke 
and gas can be consumed, that the species that abound in 
hydrogen manifest their full value. 

In positions where the radiant heat of the fire-place can 
alone be made effective, or when the volatile matter either 
escapes unconsumed, or without being applied, those kinds 
of fuel which abound in carbon, appear to be the most valu- 
able. Thus, in the very careful and accurate experiments 
made by Marcus Bull, and published in the Transactions 
of the American Philosophical Society, the values of the 
different kinds of fuel appear to be almost exactly in the 
ratio of the quantity of carbon they contain. But, upon 
examination it will be found, that all the different substan* 
Ces were experimented upon in the same apparatus, and 
that, one exactly suited to the most advantageous combus- 
tion of charcoal and anthracite. His experiments are 
therefore no more than a comparison, and no doubt a valu- 
able one, of the effects produced by the direct radiation of 
that part of the fuel which remains solid, and furnish no 
criterion of the absolute heating powers of the substances, 
when each is burnt in a furnace of the construction best 
suited to its own mode of combustion. Charcoal and an- 
thracite lose little or nothing in the form of smoke, and the 
carbonic oxide that is generated is generally completely 
burnt : this is not the case with any other species of fuel, 
unless burnt in apparatus expressly constructed for con- 
suming the smoke. We have felt it our duty to state our 
objections to the experiments of Mr. Bull, particularly as. 



COMBUSTION. 53 

in spite of these defects, they are the most valuable that we 
have it in our power to quote, especially as regards wood* 

When the hard woods, after being well dried, are sub- 
jected to destructive distillation, the residuum of solid char-^ 
coal is no more than one -fifth part of the weight of the 
wood. About one-fourth part of the volatile matter is 
condensible into the liquid form, being water, charged with 
an empyreumatic oil and acetic acid, a mixture that usually 
goes by the name of pyrolignous acid. Full one-half of 
the mass goes off in a permanently elastic form. As ana- 
lysis shows no other substances present than the three we 
have stated, and as the oxygen is principally accounted for 
in the acid, these gaseous products are probably wholly 
inflammable. Pine wood furnishes little or no pyrolignous 
acid, and a less residue of charcoal ; hence we may infer 
that when it is well dried, full three-fourths of the whole 
weight are capable of forming flame. 

When wood is employed as a fuel, it ought to be as dry 
as possible. When recently cut, it always contains a con- 
siderable quantity of water ; and as in burning it does not 
acquire heat enough to decompose that fluid, it must be 
converted into steam, which requires a considerable quan- 
tity of heat. Wood does not part with the whole of its 
moisture by mere exposure to the air, but retains at least 
one-tenth part of its weight, unless artificial heat, at least 
as great as that of boiling water, be applied. Hence, when 
wood is to produce the greatest quantity of heat which it 
is capable of affording, it ought not merely to be seasoned, 
but dried by the direct application of heat. As usually 
employed, it has about 25 per cent, of water mechanically 
combined, the whole of the heat necessary for evaporating 
which, is lost. 

Hard woods burn only at the surface ; the heat there 
generated speedily causes the volatile matters of the whole 



54 



COMBUSTION. 



mass to escape ; such of them as are inflammable take fire 
and form a flame. There soon remains nothing but a com- 
pact, dense mass of charcoal, which burns slowly and 
without flame. 

Pine and other light woods burn with much more rapidi- 
ty, as they split under the action of heat, and are besides 
porous enough to permit the air to penetrate : much of the 
carbon too either assumes a new form of combination with 
the hydrogen, or is carried ofl" in smoke ; they therefore 
leave little or no charcoal, and give out flame during nearly 
their whole combustion. 

The experiments of Count Rumford give the following 
results : 



species of wood. 

Oak, seasoned, - _ - 

dried on a stove. 

Maple, dried on a stove, - 

Fir, seasoned, - - - - 

, dried on a stove, 


lbs. of water heated 
10 by 1 Ih. of fuel. 

4590 
5940 
6480 
5466 
7150 



These are all too high for any practical purpose, as we 
rarely resort to artificial means of drying, and have but 
seldom the power of obtaining wood thoroughly seasoned. 
We therefore do not consider it safe to take at more than 
4500 lbs. the quantity of water which 1 lb. of hard wood is 
capable of heating 1°, and 5000 for the quantity heated 1" 
by pine wood. 



COMBUSTION. 



55 



The more useful of M. Bull's experiments upon wood, 
are as follows, viz : 



Ir 


Weight of 


Comp. value 


Kind of Woods 


Cord. 


per Cord. 


Shell Bark Hickory, 


lbs. 

4469 


100 


Pig-nut Hickory, 


4241 


95 


Red-heart Hickory, 


3705 


81 


White Oak, - - - 


3821 


81 


Red Oak, - - - 


3254 


69 


Hard Maple, - - - 


2878 


60 


Jersey Pine, - - - 


2137 


54 


Pitch Pine, - - - 


1904 


43 


White Pine, - - 


1868 


42 






_j 



The difference in the modes in which bituminous and 
anthracite coal burn, is still more marked than between 
various kinds of wood. Those coals which contain much 
bitumen, (as Cannel coal,) burn much like pine wood, 
sphtting and emitting an inflammable gas. Those which 
contain less, (as common Liverpool coal,) burn at first with 
flame and then leave a mass of coke or charcoal, which 
burns without flame. Anthracite, on the other hand, has 
little or no flame, except what arises from the formation 
of a portion of carbonic oxide. All coals contain more or 
less water, but much heat is not lost in their combustion 
on this account. They do not burn unless heated to a 
temperature at which water is decomposed, and in the 
flame that is formed, the two gases again combine and emit 
heat. On this account damp bituminous coal produces 
more flame than when it is dry, and although it does not 
appear to be of any use to moisten the anthracites, those 
varieties which lie in mines that are wet, are more easily 
ignited and give more flame than those which are found in 
dry situations. When bituminous coal is subjected to the 
destructive distillation, nearly two-thirds of its weight is left 



56 COMBUSTION. 

behind in the form of coke. This is principally composed 
of carbon ; a part of the volatile matter although conden- 
sible, is inflammable and will join in generating flame ; this 
with the inflammable gases amounts to about one-fourth of 
the weight of the coal, and the remainder, amounting to 
about y'j, is incombustible. 

The best anthracites contain about 95 per cent, of in- 
flammable matter, which is principally carbon. In burning 
them, however, a very considerable residue of carbon is al- 
ways left, as the interior of the pieces into which they are bro- 
ken cannot be inflamed, and the dust does not burn. This is 
not the case with bituminous coal, w^hich may have every 
particle exposed to the contact of air, by stirring it during 
combustion, and of which the smallest fragments inflame. 
If we calculate the heating powers of the two species of 
coal from their chemical composition, they will be as 
follows : 



Species of Coal. 


Lbs. of water heated 1^ 
by 1 lb. of fuel. 


Average of bituminous Coal, 


- 13792 


Anthracite, - - 


12350 


Coke, - - - - . 


- 13000 



In practice, however, a considerable quantity of heat is 
wasted, which the best experiments make about one-third, 
in the case of bituminous coal and coke, and the loss in 
anthracite from its less perfect combustion must be even 
greater. 

The results thus reduced are in the nearest round num- 
bers. 

lbs. 

For bituminous Coal, - - - 9200 

For Coke, 8600 

For Anthracite, - - - . 7800 

but the latter is probably beyond the truth. 



COMBUSTION. 57 

33. The furnaces in which the fuel employed for gene- 
rating steam is burnt, are composed of a chamber in which 
the combustible is placed, a grate on which it is laid, an 
opening through which the air enters to the fuel, and an 
ashpit, into which the unconsumed portions fall. Fur- 
naces usually receive the air from beneath and through the 
ashpit, but in some cases the air descends to the burning 
fuel, and passes downwards through the grate. In treat- 
ing of these parts we shall follow the air in its course, 
arranging them in the order in which it reaches them. 

34. The Ashpit is generally a quadrangular chamber 
enclosed on three of its sides by walls, and open on the 
fourth, which is surmounted by a bar of iron, or an arch, j 
Its section is usually of the same size as the grate, and its * 
height depends upon the circumstances of its position. It * 
ought, however, to have an opening to the free air, as large 4 
as the area of the grate. In engines placed on the land, it 
has lately been a practice, which is attended with advan- 
tage, to have a few inches of water at the bottom of the ash- 
pit ; this is renewed by a small, but constant stream. The 

air that flows to the furnaces is thus kept cool, and enters 
them loaded with moisture, which increases the length of 
the flame. In some of the more modern steam-boats the 
boilers are placed upon the wheel guards, and the space 
below the grate is open to the water beneath. The com- 
bustion is found in these cases to be more intense. There 
can be no other general rules laid down for the construc- 
tion of the ashpit, which will naturally assume its form 
from the figure and size of the furnace, and the position in 
which it is to be placed. 

35. The grate is composed of parallel bars usually of 
cast iron. They have frequently the form of a prism, 

8 



f 



58 COMBUSTIOJV. 

whose section is an isosceles triangle, the base of which is 
lowest. Their ends are rectangular and wide enough to 
keep the triangular portions at a distance of half an inch. 
When long, they are made deeper in the middle, and grad- 
ually taper to their points of support. The size of the bars 
will depend upon their length, the weight of fuel they have to 
bear, and the shocks they are subject to in throwing it in 
and stirring it. The bars are usually about half an inch 
apart, and the bars of the largest furnaces an inch and a 
half thick. The open space through which the air passes 
is therefore no more than a fourth part of the aperture on 
which the grate rests, and the space is farther diminished 
by the lodgment of the fuel upon, and the ashes and cinders 
between them. The least space that ought to be left for 
the passage of air through the grate should be equal to the 
area of the chimney, and the area of the grate itself is con- 
sequently four times as great. This, however, being the 
minimum, and the fuel and cinders opposing a resistance, 
grates ought always to be larger than four times the area of 
the chimney. We shall hereafter give the principles on 
which dimensions of this last named part of the apparatus 
depend. It is usual among practical engineers to give a 
foot of area of grate, for every cubic foot of water evapora- 
ted in an hour, when the fuel is coals, and double that space 
when the fuel is wood. This rule agrees with that deduced 
from theoretic considerations by the French and German 
engineers. In practice, however, with any free burning 
fuel, it is better to have a surface of grate beyond the abso- 
lute want, than one that may be too small. With anthra- 
cite, the case is probably different, as too large a column 
of air must diminish the intensity of the combustion. 

36. Above the grate is situated the body of the furnace. 
Its horizontal section is determined hy the size and shape 



COMBUSTION. 59 

of the grate, its depth will depend upon the nature of the 
fuel. It must, in the first place, be of sufficient depth to al- 
low such a thickness of fuel, as is best suited to its com- 
plete combustion ; and in the second, there must be, above 
the fuel, a sufficient space for the flame to be fully formed 
before it enters into the flues. 

It is very difficult to state exactly a rule for the depth of 
the fuel that lies upon the grate. The larger the masses 
in which the fuel is thrown in, the greater may be its depth. 
The depth may also be increased with an increase in the 
draught of the chimney. In all cases, fuel may be added 
until it appears to diminish the intensity of the combustion, 
for in this way the double advantage will be gained, of be- 
ing compelled to feed less frequently, and the air that 
enters will be more completely applied to the support of the 
fire. It has been found that a depth of about four inches 
is most advantageous for bituminous coal; Anthracite will 
probably require at least double that depth, and wood will 
bear even more. In respect to the quantity of combustibles, 
it is necessary that the furnace for burning wood should 
have, at least, twice the capacity of one for burning coal. 
A depth of from twelve to fifteen inches from the grate to 
the bottom of the boiler is sufficient for the most advan- 
tageous combustion of bituminous coal, while it has been 
found in practice, that if the depth of the furnace, in which 
wood is burnt, be less than three feet, the useful effect of 
the fuel is lessened. 

When high steam is to be generated, the space may be 
made less, but it is in all cases disadvantageous to bring the 
boiler into contact with, or too near to the fuel itself. The 
reason of these rules is obvious, for if the heat be with- 
drawn immediately from the fuel itself, rather than from 
the flame, and the heated air that has passed through the 
furnace, the volatile matter and heated air will cool too 



60 COMBUSTION. 

speedily, the length of the flame will be lessened, and 
much of combustible will escape unconsumed ; the draught 
of the chimney will also be diminished, by the cooling of 
the air and the absence of flame. 

In respect to furnaces placed within the boiler, they at 
first sight appear to be extremely advantageous, because, 
as the boiler itself forms their enclosure, no heat can be 
lost. But this advantage is not real, for the surface of the 
furnace being cooled down by the water to a temperature 
which in low pressure boilers does not much exceed 212", 
and, even in the case of high pressure, is far beneath the 
heat of flame, the combustion will languish, the draught of 
the chimney will be diminished, and the flame will be of but 
little length. On the other hand, it is frequently necessary 
to employ furnaces thus situated, in order to economise 
room and lessen the weight ; such is the case in steam-boats 
and locomotive engines. When such an arrangement be- 
comes necessary, the inconveniences may be in some part 
obviated by lining the furnace with fire brick, or other bad 
conductor of heat. The length of the flues may then be 
encreased, and the whole gaseous matter converted into 
flame and applied usefully. 

There are cases in which it is of advantage to burn the 
smoke that issues from furnaces. As, however, when the 
fire is properly managed, but little unconsumed matter will 
issue from a furnace of the ordinary construction, such 
plans are of very little value in making the heat produced 
by a given quantity of fuel greater. It is only, then, when 
the smoke that occasionally issues, when fuel is just added, 
is productive of inconvenience to the neighbourhood, that 
furnaces of the kind need be erected. In a general trea- 
tise, therefore, it is not considered necessary to enter into a 
detail of their construction. 

When bituminous coal is used as a fuel, it may be sup- 



COMBUSTION. 61 

plied, in proportion to its consumption by a self-acting 
apparatus, the invention of Brunton of Birmingham in Eng- 
land. This is said to lessen the expenditure of fuel rather 
more than one-third. In our country, this substance is 
rarely employed, we have not, hence, thought it necessary 
to describe it. Those who wish to become acquainted with 
its structure may consult Tredgold and Lardner. 

37. From what has been already said, it will be obvious, 
that the volatile parts of the fuel and the heated air that has 
passed through it, are not to be permitted to enter at once 
into the chimnev, but must be retained in contact with the 
boiler, at least until all the flame be made use of. The air 
and flame are therefore made to circulate in flues. These 
flues may be either beneath the boiler, upon its sides, or 
within it. Their length will depend upon the nature of the 
fuel ; when it burns with much flame they should be 
long, but if it give but little, a horizontal passage beneath 
the boiler, and of its whole length, will be sufficient. Pine 
wood will therefore require the greatest length of flue, and 
anthracite coal the least. 

The greater the periphery of the flue under a given area, 
the greater will be the quantity of heat it will give out, but 
at the same time the greater will be the friction of the 
heated air against its surface. Here again a diflerence in 
form may arise according to the nature of the fuel ; the 
flues made use of, with combustibles that furnish the great- 
est quantity of flame, having the greatest practicable peri- 
phery, while those that burn with little or no flame should 
be square or circular. This, however, applies only to flues 
beneath the boiler or upon its sides, for when the flues pass 
through the boiler, considerations of safety will generally 
require their section to be circular. 

Air being a bad conductor of heat, the bottom of a flue 



62 COMBUSTION, 

is less heated than its sides, and the latter much less than 
its top. Hence flues beneath the boiler are far more 
advantageous than those which surround it, and when a flue 
passes through a boiler, it ought, were there no other reason, 
to be entirely immersed in water. 

The whole area of the flues must not be less than that 
of the chimney, otherwise the draught will be impeded, 
and on the other hand, there is no advantage gained by 
making it greater. 

38. When the flame is completely expended, no farther 
advantage is usually gained, by making the current of air 
circulate in contact with the boiler. A part of its heat 
might, no doubt, be withdrawn, but this will be done at the 
expense of the intensity of the combustion, unless it be 
practicable to make the chimney of very great height. The 
ascent of smoke in chimneys is due to the difl"erence in the 
density of the heated air they contain, and of that of the 
open atmosphere. The force which propels the current 
is, therefore, the difference of weight of two columns, one of 
atmospheric air, the other of the heated and rarified air of 
the chimney, whose altitudes are equal, and the same as that 
of the chimney, and whose areas are equal to that of the 
aperture by which the heated aar^ enters the chimney. 
When, therefore, it is possible to make the chimney high, 
the air within it need not be as much rarified, in order to 
obtain an equal force of draught, and the flues may be per- 
mitted to circulate longer around the boiler. We conceive, 
however, that it may safely be taken as a general rule, that 
when the gas has been wholly inflamed, the heated air may 
be permitted to ascend. In furnaces for burning wood and 
bituminous coal, it frequently happens that the flame enters 
the vertical chimney and that much heat is lost ; while in 
those for burning anthracite, the flues are frequently so 



COMBUSTION. 63 

long as to diminish the draught of the chimney and the con- 
sequent intensity of the flame. 

The ascent of the air in chimneys is due, as we have 
stated, to their height and the temperature of the ascending 
column of air. But the latter is the mean temperature of 
the air in the chimney, and not that at which it enters. The 
sides of the chimney absorb heat, and it is again withdrawn 
from them by radiation, and the cooUng action of the air ; 
and hence the velocity is rapidly diminished. Air, too, is 
subject to a considerable degree of friction in the chimney. 

This last resistance is proportioned to the square of the 
velocity and the length of the chimney directly, and the di- 
ameter inversely. 

The cooling of the air depends not only upon the quan- 
tity of surface exposed, but upon the nature of the material, 
and hence experiment alone can determine the effect which 
this has upon the velocity. We are aware that the great- 
est part of the heat that is thus lost is due to radiation. 
Now, of the materials usually employed in making the 
chimneys of steam engines, sheet iron, wrought iron, and 
brick, the first is the worst and the last the best radiator 
of heat. But the difference in this respect between the two 
first is but small, and as cast iron pipes must be thicker than 
those of wrought iron, the outer or radiating surface of the 
former will be the least heated. Hence it would be rea- 
sonable to conclude, that chimneys of cast iron have the 
best draught, those of brick the worst. This has been 
found to coincide with actual experiment. 

It is extremely difficult to calculate the proper dimen- 
sions for a chimney, inasmuch as many of the elements are 
difficult to determine. Peclet has given a method founded 
upon strictly scientific principles, but it is altogether too 
complex for practice. The rule given by Tredgold, is — 
^^ Multiply the number of cubic feet of water to be evaporated 



04 COMBUSTION. 

per hour by 112, and divide by the square root of the height of 
the chimney.^^ 

This may be taken as the minimum for chimneys of brick, 
and with bituminous coal for the fuel. The last named 
author advises that the area of the chimney be made double 
as much as is given by his rule. In chimneys of iron the 
area may be less, the fuel remaining the same ; and they may 
be still further lessened w^hen the fuel is anthracite coal ; 
on the other hand, the area of chimneys for burning wood 
should be greater than those for bituminous coal. The 
best form for the horizontal section of a chimney is that of 
a circle, the friction is less in it than in any other figure, 
and in metal the cost of constructing it is less. Of figures 
having circular sections the best is the frustum of a cone, 
whose upper area is that which is given by the rule of 
Tredgold, and whose lower section has twice that area. If 
the chimney be cylindrical, a small truncated cone or conoid, 
placed upon its top, will make it act more advantageously. 

39. As various circumstances will occur, in consequence 
of which it may be necessary to alter the intensity of the 
combustion, it is customary in most cases to place a Damper 
at the junction of the flues with the chimney. This is a 
plate of iron which slides in a groove, and may either wholly 
or partially close the aperture of the chimney. Its efiect 
will be obvious, from what has been stated of the draught 
of chimneys, which depends upon their height and the area 
of the space at which the smoke enters, as well as upon the 
difference of temperature of the external and internal air. 
In speaking of boilers, a method of making Dampers self- 
acting, so as to close or open the aperture of the chimney, 
in exact proportion to the heat which is required, will be 
mentioned. 



COMBUSTION. 65 

40. It remains to speak of the doors of furnaces. These 
are usually rectangular, with hinges, and are fastened by- 
latches. The material is generally cast iron, in some cases 
cast with a flaunch within to support a lining of fire brick. 
The best of all would be a double door of iron, that when 
shut would enclose a stratum of air, but the inner shutter 
would be too liable to be destroyed by the fire. 

When cleanness and neatness is desired, the whole front 
of the furnace is made of cast iron, with apertures for the 
doors and ashpit. In reverberatory furnaces, it is fre- 
quently usual to suspend the doors by a lever, to the oppo- 
site end of which is attached a counterpoise. Such an ar- 
rangement might probably be appUed with advantage to 
the furnaces of steam engines. 

The form, arrangement, and distribution of furnaces, 
flues, and chimneys, depend, in a great degree, upon those 
of the boiler. Instances of those that are found to answer 
best in practice cannot be given, therefore, until the struc- 
ture of boilers has been examined. 



CHAPTER III. 



BOILERS. 



Materials of which Boilers are constructed. — Figure of Boil- 
ers. — Strength and Thickness of Boilers. — Apparatus for 
showing the level of the water. — Feeding Apparatus. — 
Proof of Boilers. — Safety -Valve s^ — Air-Valves. — Steam 
Guages. — Self-regulating Damper. — Common Damper and 
Register. — Dangers arising from the fire- surface becoming 
hare of water. — Thermometer. — Plates of fusible metal. — 
Valves opening at the limit of temperature. — Deposits of 
solid matter, and modes of lessening and removing them. — 
Steam-pipes. — Generator of Perkins. 

41. Water is converted into vapour, for the purpose of 
setting steam engines in action, in vessels that are called 
Boilers. These are always of metal, and three different 
materials are in use for their construction : Wrought Iron, 
Cast Iron, and Copper. Wrought iron and copper are 
rolled for this purpose into plates and sheets, which, after 
being bent to the proper form, are united by bolts, driven 
through holes punched around their edges, and riveted. 
When cast iron is used for boilers, they may either be of a 
single piece, or it may be cast in separate portions, which 
are united by screw bolts and nuts, passing through holes 
left or drilled in flaunches. Of the two first, copper is 
most easily worked, but it is far the most expensive mate- 



68 BOILERS. 

rial, and is therefore now used only in a few instances, 
where the others are, from the circumstances of the case, 
inadmissible. Copper is much4ess easily acted upon by 
oxygen than sheet iron ; it acts less powerfully upon the 
saline deposits that occur when sea or other impure water 
is used ; in addition, it is less liable, than either of the other 
materials, to split or crack on sudden changes of tempera- 
ture. 

Sheet iron is more tenacious than copper, but is liable to 
rapid oxidation and has frequently invisible joints arising 
from the manner in which it is manufactured. Still, how- 
ever, when the water used is tolerably pure, it is the best 
material, if we take into view the strength and comparative 
cheapness. 

The relative cost of boilers of the several materials may 
be estimated as follows : The comparative thicknesses of 
boilers to bear the same strain, are, 

For Copper, - - - 3 
For Sheet Iron, - - 2 
For Cast Iron, - - - 12 

The cost of them per lb. in New-York, is 

Copper, - - - 34 cts. 
Sheet Iron, - - - 16 " 
Cast Iron, - - - 6 ** 

Their respective densities according to the table §9. 

Copper, - - - 8.878 

Sheet Iron, - - 7.788 

Cast Iron, - - - 7.207 



BOILERS. 69 

The product of these three elements give their relative 
cost as follows : 



Copper, - - - - 


906 


Sheet Iron, - - - - 


- 250 


Cast Iron, - - - - 


522 


Or, taking Sheet Iron as the unit: 




Copper, - - - 


- 3.60 


Sheet Iron, - - - 


1.00 


Cast Iron, - - - - 


. 2.09 



There is another point of view under which they ought 
to be examined, which is the value of the material, after 
the boiler has become unfit for service, and here copper 
might appear to have the advantage, as it will sell for a far 
higher proportionate price than either of the others ; but 
still its depreciation in value, added to the interest on its 
cost, will be at least equal to the loss upon a boiler of 
wrought iron. 

42. In determining the proper figure of Boilers, various 
circumstances appear at first sight as necessary to be taken 
into view. 1. The power to generate steam ; 2. The ac- 
tion of their own weight to change their figure ; 3. The 
pressure of the contained fluid ; 4. The action of the steam 
to burst them. Upon a more close investigation, it will, 
however, appear, that none of these, except the last, is of 
any real importance. 

The power of a boiler to generate steam, depends upon 
the quantity of surface that is exposed to heat, and so long 
as this is the same, neither the figure of the boiler, nor the 
quantity of water it contains, have any effect upon its 
action. 



7ft 



BOILERS, 



Boilers are liable to bend by their own weight, but to 
give the top the figure of an arch, and to support the hoiler 
well from beneath, obviates all difficulty on this score, ex- 
cept in boilers of the largest kind, and the most brittle metal 
has in this respect an advantage over those which are more 
flexible. The pressure of the contained water also acts to 
change the shape of a boiler ; as this force depends upon the 
product of the surface by the depth of the liquid, it increa- 
ses with the height the liquid stands in the vessel, and 
with the developement of its sides ; and under equal depths, 
a vessel whose section is a circle will sustain the least pres- 
sure. Both of these actions may be rendered of little 
amount by distributing the water in several boilers instead 
of increasing the size of a single one. Neither of these 
influences can be compared in their amount, to the strain 
exerted by the steam which is generated within the boiler. 
This, too, varies in different species of engines. In some, 
as we shall see, the steam is condensed, and that flowing 
from the boiler acts against the partial vacuum that is thus 
formed. The steam in this case need not have an expan- 
sive force of more intensity than the pressure of the atmos- 
phere, and it, generally speaking, seldom exceeds that limit 
by more than a few inches of mercury ; such engines are 
called Low Pressure, or Condensing. In other engines, 
which are called High Pressure, the steam employed never 
has an elastic force less than two atmospheres, and more 
frequently reaches four or five. Boilers of the first 
description do not usually require materials of any great 
strength, nor is it necessary in them to seek for the form 
of greatest resistance. But in high pressure boilers, it is 
of the utmost importance, not only to use a material of suf- 
ficient tenacity, but to give them the figure which will be 
the least liable to yield under the great expansive force to 
which it is subjected. 



BOILERS. 71 

That figure which has the greatest strength to resist such 
an expansive force, is one of all whose sections are circu- 
lar. A sphere is the only solid which has this property, 
and it may be advantageously used upon a small scale. It, 
however, presents too small a surface, must have all its 
dimensions increased equally, and is not adapted to receive 
flues to retain the flame ; it is therefore never employed for 
the boilers of steam engines. 

All the sections of a cylinder at right angles to its axis, 
are also circular, it therefore presents the greatest resist- 
ance to forces acting against these sections; its ends, 
however, if plane surfaces, are comparatively weak. In 
Europe, where such boilers are of recent introduction, the 
ends are made of the same material with the body of the 
cylinder, and are formed into the shape of a portion of a 
sphere. In this country, where they have been long in 
general use, the body of the boilers is made of sheet iron, 
and the ends are plane surfaces of cast iron, made thick 
enough to be of equal strength with the other material, 
and firmly bolted to it. 

The same law that afiects the strength of a vessel to bear 
an internal expansive force, also regulates its resistance to 
a pressure from without. Hence, spherical and cylindric 
boilers resist all coUapsion, from the condensation of the 
steam they contain, better than those of other figures ; and 
hence also, when flues pass through boilers, they should be 
cylindrical. 

From what has been said §30. in speaking of the action 
of fuel, it will be obvious that the heat penetrates into the 
boiler by radiation from the burning mass, or by the direct 
contact of the flame and hot air with its surface. The ex- 
terior face of the boiler first receives the heat, it is then 
propagated in the metal by its conducting power, and it 
heats the water in contact with its interior, by causing a 



72 BOILERS. 

motion among its particles. It is clear, then, that the 
quantity of water in the boiler has no influence on the 
quantity of steam that can be formed in a given time. All 
that is necessary is, that there should be enough to cover 
the whole metallic surface, to the outside of which the heat 
is applied. Hence the quantity of fuel consumed, the ex- 
tent of the heated surface of the boiler, and the conducting 
power of the substance of which it is made, are the only 
elements that need enter into the calculation of the quan- 
tity of steam a given boiler will generate. It is better too, 
to depend upon actual experiment for the effect, than to 
deduce it from any theoretic considerations. From a mean 
of several such experiments, it has been deduced, that six 
feet of fire surface are sufficient to evaporate a cubic foot 
of water per hour. But as the flues will communicate less 
heat in proportion as they recede from the furnace, the 
sum of the surfaces, of furnace and flues, ought to be eight 
feet for each cubic foot of water to be evaporated per hour, 
for low steam, and for high steam, not exceeding five at- 
mospheres, nine feet. 

As the quantity of steam generated, depends, then, wholly 
upon the surface of the boiler that is exposed to heat, and 
as the saving of weight is in many cases advantageous, it 
has been proposed to use a combination of tubes for boilers, 
which will expose a much greater surface, in comparison 
with their internal capacity, than larger cylinders ; for it is 
a mathematical law, that while the surfaces of cylinders of 
equal length increase as the diameters simply, their internal 
capacity increases with the squares of that dimension. A 
saving may also be made in the material of which the tubes 
are constructed, for the strength of a metallic tube to resist 
an effort to burst it, increases in the inverse ratio of its dia- 
meter. It has also been proposed to immerse such tubes 
wholly in the flame, and inject into them from time to time, 



BOILERS. 73 

a certain quantity of water to be converted almost instantly 
and wholly into steam. Such were the original boilers of 
Babcock. 

The first of these plans has a speedy limit in practice, and 
the last is wholly inadmissible, as will appear from the fol- 
lowing considerations. 

1. The presence of a conducting body in the midst of 
the flame, will cool the gas of which it is composed, dimin- 
ish the intensity of the combustion, and the draught of the 
chimney. 

2. When tubes are actually heated to the proper degree, 
and no longer act to cool the flame, the flues must be made 
short enough to permit the air to enter the chimney as soon 
as it is cooled down to the temperature of the tubes, other- 
wise, instead of heating them farther, it will tend to cool 
them. 

3. The principal objection to the last plan is founded upon 
a remarkable experiment of Klaproth, which is as follows, 
viz. If a polished spoon of iron be taken and heated to a 
white heat, and a drop of water be let fall upon it, the drop 
divides at first into several smaller ones, which, however, 
speedily unite. This, if it be closely observed, will be seen 
to have acquired a rotary motion ; it continually decreases 
in bulk and finally explodQ^. A second, and a third drop 
exhibit the same phenomena, but the continuance of the 
drop upon the metal becomes less and less as the latter 
cools. One of the experiments gave the following results, 
and the others, although the absolute times of duration dif- 
fered, all exhibited a similar law. 



10 



4k«v. 



74 BOILERS. 

The first drop remained - - 40" 

The second, - - - - 20" 

The third, - . - . 6" 

The fourth, - - - - 4" 

The fifth, 2" 

The sixth, - - - - 0" 

Perkins has recently observed similar phenomena in the 
generator of his engine. This vessel being heated red hot 
while empty, water was admitted. The elastic force of the 
vapours was at first but small, and increased rapidly as the 
temperature of the generator was diminished. 

The explanation which has been given of this phenome- 
non, is as follows, viz. When it occurs, the water is never 
in contact with the metal, or at least only at a single point, 
as is shown by the spherical figure of the drops, and their 
rotary motion ; a stratum of steam intervenes, which being 
a bad conductor, does not convey heat to the drop ; and 
the expansion of the drop, out of contact with the metal, 
appears to be due to a repulsion which is exerted by incan- 
descent bodies upon those which are colder. This last ex- 
planation is corroborated by another curious fact observed 
by Perkins. He adapted to his generator, by an aperture of 
one-eighth of an inch in diameter, a tube or adjutage of three 
feet in length and half an inch in diameter within ; this tube 
was closed by a stop-cock, and the safety valve loaded with 
a weight of about 700 lbs. per square inch. The genera- 
tor being heated red hot, the steam contained in it opened 
the safety valve, but although the cock of the adjutage was 
opened, no steam escaped by it until the temperature was 
considerably lowered. 

Thus it appears, that the rapidity of the evaporation does 
not increase with the temperature of the vessel into which 



BOILERS. 75 

the water is introduced. It probably does so as long as 
the water is capable of moistening the metal, which it can _,_ 
only do before that becomes incandescent, but after the 
metal reaches a red heat, the rapidity of the evaporation j ! 
decreases with every increment of heat. ! : 

Tubes, into which the water is injected and thus convert- '""'** 
ed into steam, have this additional disadvantage : the de- 
posits of solid matter that fall from almost all water when 
evaporated, and which are greater in proportion as the 
water is impure, become harder and more compact than 
when the boiler is kept full of water ; they also adhere 
more forcibly to the metal, and are more liable to corrode it. 

This method, however, has the advantage of being free 
from all risk of explosion, and there are of course cases 
where this advantage may be worth obtaining, even at the 
sacrifice of a considerable quantity of heat. 

It has been proposed in this country, and we have seen 
it practised in several cases, to adapt to the lower part of 
boilers, tubes communicating with them, and immersed in 
the flame. Such, too, was the form proposed by Woolf 
in England. Actual experiment has shewn that such an 
addition has no real advantage, and when the tubes are 
constructed of cast iron, they run the risk of being broken 
by the sudden variations in temperature to which they are 
exposed. It may, therefore, be inferred, as a general rule, 
that it is better to use cylindrical boilers of at least a foot 
in diameter, than tubes of small size, whether alone, or 
communicating with larger vessels. 

43. We have stated that the most important force to 
which boilers, and particularly those containing high steam, 
are exposed, is the expansive energy of the steam itself. 
The action of this force upon the sides of a cylinder is pro- 
portioned to the elastic energy of the steam, and the radius 



7e 



BOILERS. 



of the cylinder ; and it is resisted by the cohesive force of 
the metal. 

If the ends be a portion of a sphere whose radius is equal 
to the diameter of the cyUnder ; then the strain upon any 
given surface is equal to that upon the sides. 

When the ends, as is usual in this country, are plates of 
cast iron, their strength is investigated upon the principle 
of a beam, equally loaded throughout its length, and sup- 
ported at the ends. The force that will break it, is propor- 
tioned to the square root, of the pressure, multiplied by the 
square of the diameter. 

The absolute weight which a cubic inch of the usual 
materials will bear without breaking is, for 



Bar Iron, . 


- 64000 


Sheet Iron, 


- 57000 


Cast Iron, 


- 19000 


Sheet Copper, 


- 40000 



It is not, however, sufficient that the boiler does not break 
under the expansive force, it must not even change its 
figure, nor must the bolts by which it is fastened give. 
These materials are in consequence much nearer in value 
than their absolute strengths would show, for cast iron will 
bear 153001bs. per cubic inch, without changing its shape, 
and wrought iron no more than 1 78001bs. 

The change of figure that each will support without 
breaking, is also very different ; in cast iron, the hmits of 
expansion and fracture are very near to each other ; sheet 
iron will stretch before breaking from j\ to ^\ ; while 
copper may be expanded f ths of its original dimensions. 
Another circumstance also must be taken into account, 
which is their respective liabilities to break by sudden 



BOILERS. 



77 



changes of temperature ; to this cast iron is very liable, 
sheet iron but little, and, copper not at all. Taking all these 
circumstances into account, we have assumed as the num- 
bers proper to represent the strength of these materials* 



Sheet Iron, - 
Copper, 
Cast Iron, 



lbs. 

9000 
6000 
30C0 



M^^^ 



n 



The first being about half the strain that wrought bears 
without changing its figure ; the other two bearing the 
nearest ratio to it in round numbers, that their respective 
strengths do. 

It is also to be taken into view, that the tenacities first 
given are estimated from experiments made upon the 
metals when cold, while it may occasionally happen that - 
parts of the boiler reach a red heat. Now it has been tA^^ 
found from actual experiments that the tenacity of metals 
may be diminished by heating them red hot to not more than' 
a sixth-part of that which they possess at an ordinary tem- 't 
perature The numbers last given are reduced from the*^^ 
first in even a greater ratio, and therefore are sufficiently 
small to make full allowances for this decrease of strength. 

The rules for estimating the thickness of the plates of 
which cylindrical boilers are made is as follows : 

Multiply the Radius in inches by the pressure on each 
square inch in lbs. and divide the product by the number as- 
sumed above as the strength of the material, the quotient is 
the thickness in inches. 

The rules for the ends are as follows ; . 

If of the same material with the body of the cylinder, the 
ends, if hemispherical, need only be half as thick ; if a portion 
of a sphere whose radius is equal to the diameter of the cylin- 







78 



BOILERS, 



der, the two thicknesses are equal. If of any other radius^ 
multiply half the radius in inches by the pressure in lbs. and 
divide by the cohesive force of the material. 

If the ends be plates of cast iron. 

Multiply the pressure on each square inch in lbs. by the 
square of the diameter in inches, and divide the product by 
twice the cohesive force of the material, the square root of the 
quotient is the thickness in inches. 

Such are the rules which theoretic considerations would 
point out. We shall proceed to compare their results for a 
pressure of lOOlbs per square inch, with the practice of 
the best engineers of this country, in cylindric boilers of 
sheet iron with cast iron head. 












1 






1 




Diameter of 
Cylinder. 


Thickness of 
Sheet Iron. 


Thickness of 
Cast Iron Heads. 


Calculated. 


Used. 


Calculated. 


Used. 


in. 

18 


in. 

0.1000 


in. 

0.1875 




in. 
1. 




24 


0.1333 


0.1875 




1.25 




30 


0.1667 


0. 250 




1.25 




36 


O.20O0 


0. 250 




1.50 




42 


0.2333 


0. 250 




1.50 



The labour of bending and shaping thick boiler plate is 
so great, and the imperfections of sheet iron increase so 
rapidly with its thickness, that, as a general rule, it may be 
stated, that the diameter of cylindrical boilers, for high 
pressure steam, should not exceed 30 inches. There are, 
however, exceptions to this rule, in the cases of steam- 
boats and locomotive engines, where it is usual to carry the 
flues through the boiler. 

When flues are thus situated, the same reason, that leads 
to a preference of cylindrical boilers, would point out that 
the form of the flues should be of that figure. The same 



BOILERS. 79 

rules may be adopted for estimating their thickness. In all 
other cases it is better to increase the number of boilers, 
than to increase their diameter, and even in these, we can- 
not help being of opinion that there is never any absolute 
necessity for carrying the flues through the boiler. 

An increase in the number of boilers rather than an in- 
crease in the diameter of a single one, has this farther 
advantage, that the weight of water will be much less than 
in the latter case. In increasing the diameter, the quantity 
of water, (the length of the cyhnder remaining the same,) 
will increase with the square of the diameter, while the 
surface exposed to heat only increases as the diameter 
simply. A cylinder of twice the diameter will* therefore 
carry twice as much water as two separate cylinders, while 
it has only the same capacity for generating steam. From 
what has been said, it may be inferred, that sheet iron is the 
best material, and a cylinder the best shape for boilers in 
all usual cases. When sea water is used, copper is, how- 
ever, the only one of the three materials that can be de- 
pended upon to resist the action of the saline deposit. In 
low pressure engines, the cylindrical form is rarely used, 
although it has advantages even in this case. The more 
usual form is to contract the vertical section upon a rec- 
tangle, by describing a semicircular arc upon its upper side, 
forming a convex arch, and three less circular arcs within 
the remaining three sides, forming curves concave to the 
exterior. The lower arc is exposed to the fire, the two 
on the sides afford space for the return flues on the out- 
side of the boiler. See PI, /., Fig. 2. 

44. When boilers have been filled to the proper height 
with water, they will require a supply, equivalent to the 
quantity of liquid that is carried off* in the form of steam. 
This supply may be either admitted from time to time by 



80 BOILERS. 

the engineer, when the water has fallen to a certain con- 
ventional level, or it may be introduced by a self-acting 
apparatus in such a manner as to keep the water at a con- 
stant height. 

In the first case, it is indispensable that the fireman or 
engineer should have it in his power, at any instant, to de- 
termine the height at which the water stands in the boiler ; 
and although the apparatus for this purpose is not indispen- 
sable when the boiler is supplied by one that depends for 
its action upon the state of the water itself, it is still a valu- 
able check upon the operation of the supply, and should 
therefore be adapted to all boilers. 

The most usual and most ancient contrivance for this 
purpose, consists simply of two stop-cocks ; each of these 
is attached to a short tube ; one of them communicates 
with the boiler below the level at which it is wished to retain 
the water, the other enters it above that height. If the 
former of these be opened and steam issue, water must be 
immediately supplied ; if the latter give out water, the liquid 
stands too high- These tubes, in boilers where the steam 
has an elastic force little exceeding the pressure of the 
atmosphere, must be introduced horizontally into the sides 
of the boiler ; but where high steam is used they may rise 
vertically through its top, and afterwards bent in a horizon- 
tal direction. See PI. /., Fig, 5 and 6. 

The best apparatus for this purpose, in all the cases where 
it can be employed, is a straight glass tube, open at both 
ends, which are placed in two cylindrical cups, that com- 
municate at the side with the interior of the boiler. To 
these cups the tube is cemented, and the water will stand 
in it at the same height that it does in the boiler. But this 
simple method cannot be used with safety in high pressure 
boilers, nor can it be adapted to any made of other material 
than copper. 



BOILERS. 81 

Another mode is to adapt a tube, made like the pipe of 
an organ, to the boiler, the lower end of which descends 
as far as the level, below which the water ought not to be 
permitted to fall. So soon as the water does descend the 
least space below this point, steam will escape through the 
pipe, and give warning of the necessity for a supply by the 
sound it causes. In high pressure boilers, this tube cannot 
be applied, as it would become of inconvenient length. 

If a substance of convenient form, denser than water be 
taken, and be made to communicate with a lever without the 
boiler, by means of a wire passing through a stuffing box, 
it may be made just to float at the surface of the water by 
a counterpoising weight, suspended from the opposite end 
of the lever. When the water falls the floating substance 
will preponderate, and the lever will incline towards the 
wire ; when the water is too high the inclination will be in 
the opposite direction ; and these deviations of the lever 
from the horizontal position, may be marked by an index 
at right angles to it, and affixed to its centre of motion. 

45. The boiler may be supplied as often as appears ne- 
cessary from the indications of either of these apparatus, 
by different means, that must vary according to the elastic 
force of the generated steam. If the steam have a force 
but little greater than an atmosphere, a simple tube, having 
a top shaped like a funnel will answer the purpose. This 
must be inserted into the boiler through a steam-tight joint, 
until it nearly reaches the bottom, and it must be high 
enough to contain a column of water, equivalent to the 
excess of the power of the steam over the atmospheric 
pressure. The steam being at a constant elasticity, the 
water will stand in this tube at a constant height above the 
level of the water in the boiler, and if water be poured 
into it, an equal quantity must pass into the boiler. To 

11 



82 BOILERS. 

adapt this to high pressure engines, a tube of inconvenient 
length would be necessary ; recourse must therefore be had 
to other means. 

The most simple of these is a spherical vessel, connected 
with the boiler from beneath by a tube and stop-cock, and 
closed at top by another stop-cock, surmounted by a fun- 
nel. The lower stop-cock is first closed, and the sphere 
filled through the funnel and upper stop-cock ; the upper 
stop-cock is then shut : and, when it is known that the 
boiler needs a supply, the lower stop-cock is opened, 
through which the water will now pass to the boiler. The 
alternate action of these stop-cocks, in the first instance, 
prevents the steam from escaping and from interfering with 
the entrance of the water ; and, in the second, permits 
the water to enter the boiler, which is replaced by steam. 
See PI. 11., Fig. 2. 

The operation of such an apparatus may be facilitated 
by making two parallel passages through each of the cocks. 
One of these is in each made, when the stop-cock is open, 
to adapt itself to a tube, which reaches from each stop- 
cock nearly to the opposite side of the spherical vessel. 
When the upper stop-cock is opened, the water will enter 
through the tube, and the enclosed air or steam will escape 
at the other passage of the cock. When the lower stop- 
cock is opened, the water will rush through the naked 
opening, and steam rise to replace it through the tube. 

A forcing pump may also be used to supply high pressure 
boilers, the pressure on the piston of which must be greater 
than the elastic force of the steam. A valve, by which the 
water the pump propels, may be made either to enter the 
boiler, or run to waste, at pleasure, will then supply the 
water that may be needed. See PL IV., Fig. 6. 

In all cases, however, it is better that the feeding appa- 
ratus should be self-acting, or, to speak more properly. 



BOILERS. 83 

should be governed in its operation by the level at which 
the water stands in the boiler. 

For low pressure engines, the construction of such an 
apparatus is attended with but little difficulty. 

The most obvious and simple of all, and it is equally ap- 
plicable to high and low pressure boilers, is a ball floating 
on the surface of the water, and attached by an arm to a 
stop-cock upon the supply pipe. This stop-cock is opened 
when the ball falls, and shuts when it rises. It may be at- 
tached in a low pressure boiler to a pipe, of a length suffi- 
cient to bear a column of water equivalent to the excess of 
the force of the steam above an atmosphere, but in a high 
pressure engine it must be adapted to the pipe proceeding 
from a forcing pump. 

This method is liable to the objection of being subject to 
get out of order, and of being out of sight and reach; it 
may, therefore, fail at the moment it is least expected. 

The floating ball may be made to act, through the inter- 
vention of a lever and a rod, upon a conical valve in the 
feed-pipe. 

A floating apparatus similar to that which has already 
been mentioned for indicating the level of water in the 
boiler, may be made to regulate the supply of a low-pres- 
sure boiler. In the first place, the lever there described, 
may have its centre of motion in the axis of a stop-cock to 
which it is attached. In the second place, a conical valve 
may be attached, by a rod, to the arm of the lever that 
carries the weight. Around this rod is a small reservoir 
of water, communicating with the boiler beneath by a 
pipe reaching nearly to the bottom. The conical valve is 
adapted to the junction of this pipe with the reservoir in 
such a manner as to open the communication when the 
float falls, and close it when the float rises. See PL II. 
Fig 8. 



84 



BOILERS. 



Another application of the same principle is represent- 
ed beneath. Here the float is lighter than water, and the 
friction of the stuffing box is avoided. 




iiii...ium.^nmnHnmi,jmmiu.jii.uMi;n.ii 



The supply of high pressure boilers, as has already been 
stated, is usually effected by means of a forcing pump. 
See PL IV. Fig, 6. 

This propels, by the action of the piston a 6, a stream of 
water into a pipe furnished with two stop-cocks or valves, 
c and d, that act alternately ; by one of these, c, water is 
admitted into the boiler, by the other, d, it is allowed to run 
to waste. These valves are usually left to the care of the 
engineer, as an apparatus to render them self-acting is ne- 
cessarily complex. We, however, give a drawing of one, 
the invention of a Mr. Franklin, that has received the 
medal of the British Society of Arts. See PL II. Fig. 1. 



BOILERS. 85 

All feeding apparatus should be sufficient to supply the 
boiler with considerably more water than it usually evapo- 
rates. Generally speaking, it is made to furnish five or 
six times as much, as it is far better that water should run 
to waste, than that there should be at any time a want of a 
full supply. 

It will be obvious, that a self-acting feeding apparatus 
that will act when the engine is at rest, is still a desidera- 
tum for high pressure boilers. It is in the case of steam- 
boats and locomotive engine that such an apparatus is 
almost indispensable, in order to place them wholly beyond 
the reach of danger, and to the want of it, by far the greater 
number of fatal explosions that have occurred, are to be 
attributed. 

46. A regular supply of water is not only necessary to 
keep up the flow of steam but is of great importance to 
the safety of a boiler ; we have, therefore, treated of it next 
in order to the material. 

Whatever precautions may be taken in the choice and 
adjustment of the strength of the material, and in giving a 
regular supply of water, it is indispensable, before a boiler 
is made use of, that it should be proved. This is necessary, 
because, the proof shows defects that would otherwise 
escape notice, particularly at the joints of the wrought 
metals, while in cast iron there are frequently cavities that 
are not seen upon the surface. These different defects 
might cause a boiler to burst with violence, if it were to be 
subjected to the action of steam, before proof had been 
performed in some other manner. This preliminary proof 
is best effected by means of the hydraulic press, or water 
pressure pump of Bramah, whose principle has been ex- 
plained on page 19. This method is, however, still defec- 
tive, inasmuch as it must be performed, if not with cold 



86 BOILERS. 

water, with that which is far below the heat to which parts 
of the boiler must be afterwards subjected. 

It has been proposed to apply a pressure five or six 
times as great as the boiler is intended to bear. Nor is 
this too great a precaution, for the water proof is performed 
when cold, and we have seen that the metal is then more 
tenacious than when heated, and the proportion of six to 
one, at least, is necessary before this difference is obviated. 
If a boiler be not subjected to such a proof, it may be 
possible that when heated its limit of rupture may be reach- 
ed, before the safety valve opens. 

The water proof having been performed, the boiler should 
next be subjected to a similar trial by steam, say of twice 
the force that is usually to be generated in the boiler with- 
out causing its safety valves to act. In France, it is re- 
quired by law, that all high pressure boilers be subjected to 
a proof, five times as great as the boiler is intended to bear, 
when in service. 

47. The next precaution to be taken is, that the boiler 
be furnished with safely valves. A safety valve is a conical 
or cylindrical stopper inserted in a seat of the same shape, 
and kept in its place by a weight, equal to the most intense 
pressure that is intended to be exerted upon it by the va- 
pour, from within the boiler. When the steam acquires a 
force greater than this, the safety valve will open and per- 
mit the steam to escape ; at all inferior temperatures it 
will remain shut. Three things must therefore be inves- 
tigated in order to their preparation, viz : the size of the 
opening to which they are adapted, the load they are to 
bear, and the most proper mode of placing them. 

The openings must be large enough to permit all the 
vapour that can be formed to escape. This may be estimat- 
ed at the conversion into steam of a cubic foot per hour 



BOILERS. 87 

from every eight or ten feet of fire and flue surface. But as 
the safety-valve will probably be most needed, when the fire 
has been augmented beyond its proper quantity, it will be 
well to prepare for the escape of, at least, four times that 
quantity, say a cubic foot of water evaporated for every 
two feet of fire surface ; this is the maximum of steam that 
can be formed under any circumstances. 

The vapour will escape with a velocity that will depend 
upon its elastic force, but which increases much less rapidly 
than that does. We subjoin the velocities under different 
expansive forces. 

Table of the Velocity of Steam at different temperatures. 



1 










■nl 


Expansive 


force. 








Velocity per second. 


u 


Atmospheres, 


- 


- 


- 


- 873 


If 


do. 


. 


. 


. 


- 1145 


ll 


do. 


. 


. 




- 1296 


2 


do. 


- 


> 


- 


- 1405 


3 


do. 


^ 


. 


- 


- 1548 


4 


do. 


• 


. 


. 


- 1663 


5 


do. 


- 


- 


. 


- 1725 


6 


do. 


. 


- 


. 


- 1785 


8 


do. 


- 


- 


. 


- 1852 


10 


do. 


. 


. 


- 


- 1993 


12 


do. 


- 


- 


- 


- 2029 


14 


do. 


. 


- 


- 


- 2052 


16 


do. 


. 


. 


. 


- 2072 


18 


do. 


. 


- 


. 


- 2084 


20 


do. 


- 


- 


- 


- 2098 



The quantity obtained, by multiplying these velocities by 
the area of the opening to which the valve is adapted, 
must be diminished by the constant fraction that represents 
the section of the vena contracta in fluids ; this, in such an 
orifice, is about |ths or .75. 

To determine the quantity then, that will issue by a given 
safety valve, three-fourths of its area must be multiplied by 



88 BOILERS. 

the velocity under the anticipated expansive force. When 
the quantity to be discharged per second is given, the re- 
verse of the operation will give the proper area of safety 
valve. The bulk of steam generated by the evaporation of 
any given quantity of water, may be found, by multiplying 
the bulk of the water by the number representing the 
volume of steam of that temperature, on page 35. 

The weight, with which the upper surface of a safety 
valve is to be loaded, should be equal to the pressure which 
the vapour, at the maximum temperature for which the 
boiler is calculated, is capable of exerting, upon the lower 
side of the safety valve. When this expansive force of the 
steam, at the given temperature, is estimated in atmospheres, 
one atmosphere, or 151bs. per square inch, is to be deduct- 
ed from the estimate, inasmuch as the escape of the steam 
is opposed by pressure of the atmosphere itself, which 
therefore acts as a part of the weight with which the safety 
valve is loaded. Therefore to find the weight : 

The area of the safety valve in square inches must he muU 
tiplied by 15 times the number of atmospheres, to which the 
expansive force of steam at the given temperature is equivalent, 
less onCf the product is the weight in pounds. 

The weight in most cases acts upon a lever of the se- 
cond kind, by the intervention of which the pressure is in- 
creased. As the foregoing rule gives the pressure that 
ought to act upon the safety valve, the weight that is sus- 
pended from the lever must be diminished, in the ratio by 
which the whole length of the lever exceeds the distance 
between the fulcrum of the lever, and the safety valve. 

The number of atmospheres, to which the expansive 
force of steam, at different temperatures, is equal, may be 
found by the table upon page 34. 

There is a curious phenomenon which occurs when 
steam issues from a safety valve, or other orifice ; the tem- 



BOILERS. 89 

perature of the vapour just without the opening, is lower, 
the higher th« tension of the steam is within the hoiler. 
Thus steam issuing from a boiler, the water within which 
is at 212% scalds the hand, while if it had a tension of seve- 
ral atmospheres, the heat would be easily borne without 
injury. This phenomenon, which at first sight appears al- 
most paradoxical, grows out of the rapid dilatation of dense 
steam, and the consequent increase of its capacity for 
specific heat. The greater the tension, and consequent 
density of the steam, the greater will be the diminution of 
temperature. 

Safety valves, generally speaking, are of the figure of a 
frustum of a solid cone, ground to fit a hollow frustum of 
an equal hollow cone. They may, as has been stated, be 
pressed down by a weight, acting directly, or through the 
intervention of a lever. In the former case, the weight 
may either hang from the valve within the cylinder, or be 
fastened to its exterior surface. A valve of this description 
furnishes a constant pressure, and ought to be adapted to 
the highest temperature the boiler is intended to bear. If 
it act by means of a lever, the pressure of the weight, when 
at the extremity of the lever, ought to be equal in its action 
to the same maximum tension; but, by making it act nearer 
to the fulcrum, its action may be made equivalent to the 
expansive force of steam of lower temperatures. The lat- 
ter is, therefore, best adapted to the case where the action 
of the boiler is left to the discretion of the fireman ; while 
those where the weight acts directly, may be enclosed and 
kept beyond his reach. 

On Plate I. are to be seen several varieties of the safety 
valve. Fig. 10, is a conical valve, whose weight is sus- 
pended beneath it, and hangs within the boiler. Fig. 11, 
is one, also conical, whose weight lies above it, and without 
the boiler. Fig. 12, is another of the same shape, and bear- 

12 



90 BOILERS. 

ing a weight upon it, which is enclosed in a cylinder, in 
such a way that it may be shut up beyond the reach of the 
workmen. Fig. 13, is a cylindrical safety valve, working 
in a pipe and pressed down by a spring ; when the pressure 
of the steam overcomes the elasticity of the spring, the late- 
ral openings in the pipe are uncovered in succession, and 
the space for the escape of steam increases with its tension. 
A safety valve, pressed down by a lever bearing a weight, 
is represented upon PL IL at Fig, 7. 

In all boilers, there ought always to be two valves, one 
of which is left to the care of the fireman or engineer, the 
other fitted to the intended maximum pressure of the 
contained steam, and closed up. Very serious accidents 
have frequently occurred, from leaving safety valves 
wholly to the control of a workman, or even of the cap- 
tains of steam vessels, who may feel a temptation to in- 
crease the pressure of steam, beyond what the boiler is 
capable of bearing. The proper situation of the safety 
valve is upon the top of the boiler : and when there are 
two, one should be at each end ; that left to the discretion 
of the workmen at the end next the fire, so as to be within 
their reach, that which is beyond their control at the far- 
ther extremity. When the aperture, by which the boiler is 
entered for the purpose of cleansing it, is situated on the 
top, the safety valve is often placed in its cover. 

In consequence of a remarkable fact that has recently 
been observed, much doubt has existed as to the certainty 
of the action of a safety valve. When air is strongly com- 
pressed, in a vessel or pipe, and issues thence by an orifice 
in a plane surface, if a plate or disk be presented to the ori- 
fice by one of its plane surfaces, so far from being driven 
away, it will be retained at a very small distance from the 
orifice. In this case, the air escapes in the form of the 
surface of a very obtuse angled cone around the edges 



BOILERS. 91 

of the disk, having a conical vacuum beneath, and in 
consequence of the well known fact, that there is a lateral 
communication of motion from a current of a fluid to neigh- 
bouring portions of the same or other fluids, the air above 
the plate moves towards it in order to join the stream ; 
the vacuum beneath, and current from above, united, 
retain the disk at a constant, but small distance, from 
the plane in which the orifice is pierced. It has been found 
that the escape of steam is attended-with similar phenome- 
na. Still, however, in conical safety valves, if thin, there 
is no reason to apprehend any danger from this source. In 
those of the usual form, the increased resistance growing 
out of this cause, will not exceed one-twentieth of an at- 
mosphere, or three-fourths of a pound upon each square 
inch. But were the valve to have the form of a frustum 
of a cone, whose height is great in proportion to the aper- 
ture, the resistance might become enormous, and, in the 
case of some experiments that were made in reference to 
this subject, it amounted to upwards of thirty atmospheres. 

However carefully a safety valve may have been con- 
structed, it may notwithstanding cease to act, in conse- 
quence of rust, v/hich will fix it to its seat. This is much 
more likely to happen when it has been long shut, but may 
occur even to valves in frequent action. Still, however, 
to open the valve from time to time, is the best preventa- 
tive, for a safety valve, that has remained closed for a week, 
no longer deserves the name. 

Large boilers of but little strength, as employed for gene- 
rating low steam, are sometimes exposed to a danger of 
an opposite nature. When the fire is extinguished, the 
steam within will be condensed and a partial vacuum form- 
ed, the external atmosphere will now act, and may cause 
the boiler to collapse. It has been proposed to remedy 
this defect by an air valve. A conical valve opening in- 



92 BOILERS. 

wards, and kept in its place either by a counterpoise, or a 
weak spring ; if either of these be little more powerful 
than the weight of the valve itself, they will keep it in its 
seat, so long as the tension of the steam within exceeds 
that of the atmosphere ; but when the latter becomes the 
most powerful, the valve will open and admit air. 

49. Lest the safety valve or valves, should by some ac- 
cident become fixed to their seat, it is important that there 
should be some means of determining, at any moment, the 
elastic force of the steam within the boiler. Apparatus for 
this purpose are called Steam Guages. The simplest form 
of these, is a bent tube, the two branches of which are par- 
allel ; one of these branches is open to the air, the other is 
bent in such a manner as to be adapted to an opening in 
a part of the boiler above the level of the water it contains, 
or to the steam pipe, and is soldered or sealed to it in 
such a manner, that steam cannot escape by the joint ; this 
tube, if empty, would permit steam to escape through it, 
but mercury is poured in to fill the bend, and rise some 
inches in each branch of the tube. When the expansive 
force of the contained steam is just equal to an atmosphere, 
the mercury will stand at equal heights in each branch of 
the tube ; when the pressure increases, the level of the 
mercury, in the branch nearest the boiler, will be depress- 
ed, and that in the open branch raised ; the sum of the 
two equal changes of level will be the measure, in inches of 
mercury, of the expansive force. As the changes of level 
in the two branches are equal, it is sufficient to measure 
that of the outer tube alone ; this is done by a scale on the 
side, if the tube be of glass, but if of iron, by placing in it 
an iron rod which floats upon the mercury ; and which just 
reaches the top of the tube, when the two columns of that 
fluid are of equal height. The tube, or rod, is graduated 



BOILERS. 93 

by division into half inches, each of which corresponds to 
a difference in the two levels of a whole inch, the thirtieth 
part of an atmosphere, or half a pound upon each square 
inch of surface, over and above one atmosphere. Were 
the guage to be graduated to inches, each inch would cor- 
respond to one pound of internal pressure, against the 
weight with which the safety valve is loaded. A guage of 
this form is represented on PL /., Fig, 7. By adding to 
the length of both branches of the tube, making it of a 
strong material, and increasing the quantity of mercury, 
this guage may be fitted for steam of any elastic force, but 
it might in that case become inconvenient to observe its in- 
dication by means of a graduated rod. In such cases, a 
float of iron may rest on the surface of the mercury in the 
open branch, and be attached, by a cord passing over a 
pulley, to a counterpoise ; the ascent and descent of 
which, along a graduated scale, would mark the difference 
of level, upon the same principle as the rod. 

A straight tube, inserted nearly to the bottom of a close 
cistern, that communicates at top with the steam of the 
boiler, and which contains a mass of Mercury, will also 
answer this purpose. If the surface of the cistern be large 
in proportion to the area of the tube, the change of level 
within it may be neglected, and the height of the mercury 
in the tube measured in inches. See Plate I. Fig. 8. 

The steam guage may be made to act as an additional 
safety valve. In this case its height must not exceed that 
which will measure, in a column of mercury, the maximum 
pressure the boiler is intended to bear, and the top must be 
widened into the form of a funnel, sufficiently large to 
contain all the mercury with which the tube is supplied. 
Such an apparatus, with the arrangement of float and 
counterpoise sliding in a scale, is represented PI. I. Fig. 8. 

A guage for a high pressure boiler may be made by im- 



94 BOILERS. 

mersing the lower end of a glass tube in a basin of mer- 
cury ; the upper end of the tube is closed, and it contains 
atmospheric air. The basin of mercury is enclosed in a 
case communicating with the boiler. The steam, acting on 
the surface of the mercury, will force it up the tube and 
compress the air, and the space that it occupies, being 
according to the law stated on p. 24, inversely as the pres- 
sure, will show the tension of the steam. Such a guage 
is represented at Fig. 8, on PL L 

50. Should the fire be more intense than is consistent 
with a regular supply of steam of the required temperature 
and pressure, an apparatus has been contrived to moderate 
its action, by the very increase in elastic force which it com- 
municates to the steam. This is called the self-acting or 
self-regulating damper. Hitherto they have only been ap- 
plied to boilers, containing steam of so small an elasticity 
as to be capable of being supplied with water by an open 
feed-pipe, as described § 45. 

The water stands in this pipe, at a height above that in 
the boiler, which depends on the difference between the 
elastic force of the steam, and the pressure of the atmos- 
phere. A plate of iron, sliding in a vertical groove at the 
throat of the chimney, is attached a float resting on the 
surface of the water in the feed-pipe by a cord passing 
overpullies; when the float rises by an increased action 
of the steam, raising the water in the feed-pipe, the damper 
will descend, and when the float descends, the damper will 
be raised. It will, in the former case, lessen, and in the 
latter, increase the aperture of the chimney, and the 
draught will vary with the size of the aperture, as has al- 
ready been stated. Such an apparatus is represented as 
attached to the boiler, Fig, 1, PL I, n is the float, o the puUy. 



BOILERS. 95 

51. In addition to a self-regulating damper, there should 
be another, to be worked by hand as occasion may require ; 
and in order to place the fuel completely under the control 
of the fireman, the passage by which air is admitted to the 
ashpit, ought also to be capable of being opened and shut 
at pleasure. Doors and valves for this purpose should 
therefore be provided, and the apparatus is called a Regis- 
ter. 

52. There are dangers, however, to which boilers are 
exposed, against which safety valves and self-acting 
dampers present no security, and of which steam guages 
give no notice. As a general rule it is no doubt true, 
that the temperature and tension of vapour bear a con- 
stant relation to each other; but it may so happen that 
steam, after being generated, is raised to a high tempera- 
ture without exerting a proportionate expansive force. 
Thus if a portion of a boiler should acquire a heat greater 
than the water contained in the other parts, as it may do 
when not covered with water, the steam will receive an 
excess of heat without acquiring a proportionate elasticity. 
In experiments made by Mr. Perkins, steam was heated to 
a temperature at which, if of a corresponding density, it 
ought to have exerted a force of 56000 lbs. per square 
inch, but which did not exert a pressure of more than 150 
lbs. The reason is obvious, for it was enclosed in a sepa- 
rate vessel, and its quantity remaining constant, it did not 
increase in density. Had, however, a small additional 
quantity of water, heated under pressure to a high tempe- 
rature, been injected, it might be inferred, that the steam 
would have acquired the density, necessary to enable it to 
exert the force corresponding to its temperature. Perkins 
also established the truth of this inference, by actual experi- 
ment. Water was heated in one of his generators, the 



96 BOILERS. 

safety valve of which was loaded with a weight of GO atmos- 
pheres, to a temperature of upwards of 900°; a receiver 
was prepared, void of both air and steam, and heated to 
upwards of 1800" ; a small quantity of water was then 
made to pass from the generator to the receiver ; this was 
instantly converted into steam, whose heat was sufficient ta 
inflame the hemp that coated the tube, <at a distance of 10 
feet from the generator; its temperature was therefore 
estimated at not less than 1400° . In spite of this high tem- 
perature at which the steam was formed, its pressure did 
not exceed five atmospheres. But by injecting more water, 
although the temperature was lessened, the elastic force 
was gradually increased to 100 atmospheres. In phenome- 
na of this description we may find the cause of many ex- 
plosions that cannot be explained on any other principle. 

If we suppose, that the supply of water is impeded or 
checked altogether, the level of that in the boiler must de- 
scend, and parts exposed to the action of the fire may be- 
come dry ; such parts may then be heated far beyond the 
temperature of the water beneath ; and the vapour may be 
rendered by them sufficiently hot, to make other parts of 
the boiler luminous. If by any cause, the water from be- 
neath be brought into contact with the vapour and heated 
surfaces of the boiler, it will be instantly converted into 
steam of great expansive force, and in quantities for which 
the usual safety valves are not sufficient to provide an 
escape. An explosion must therefore ensue. 

The water may be brought into contact with these heated 
parts of the boiler, or with the hot vapour, by the very 
means that in other cases would be applied to diminish the 
danger. Thus if the safety or throttle valve should be 
opened, the water, which was before boiling quietly, will 
suddenly rise with violent ebullition, or if the feeding ap- 
paratus begin again to act, the level of the water will be 



BOILERS. 97 

raised. In both cases, a contact will take place with the 
red hot surfaces, and with the intensely heated steam. 

This is in truth almost the sole cause of the explosion of 
boilers, whether of low or high pressure. When they give / 
way under the force of the steam alone, dangerous con- 
sequences appear to have rarely happened. We have 
ourselves been twice in steam-boats, working with steam 
of not less than an atmosphere and a half, when the boiler 
has given way, and in neither case was the accident known 
to the passengers, except by the stopping of the machinery. 

The wrought iron boiler of a high pressure engine, work- 
ing with steam of the tension of six atmospheres, gave 
way recently in a manufacturing establishment in the ; 
city of New-York, and the only bad effect was the extinc- 
tion of the fire by the efflux of the water. 

At Paris, the lower part of a boiler of cast iron, working 
with steam of the same force, gave way, and no other bad 
consequences followed. 

In all cases, where fatal accidents have occurred, the ex- 
plosion appears to have been due to other causes, than the 
mere expansive force of the steam that would be formed 
when the boiler is in proper order and supplied with water. 

In the late fatal accidents of the Chief Justice Marshall 
and Helen McGregor, the explosions took place after delay, 
at stopping places, and followed almost instantly the open- 
ing of the throttle valve, to set the engine again in motion. 
In the former, where the main internal flue gave way, the 
safety valve was either open, or had just been closed ; one 
of the persons on board remarked a peculiar shrillness in 
the sound of the escaping steam, that can only be ascribed 
to its being intensely heated, without having a correspond- 
ing density ; another observed that it had a violet hue, 
which may perhaps be explained by supposing it to have 
been heated until it would have been luminous by night. 

13 



^8 BOILERS. 

In opposition to the opinion that the water had fallen too 
low and left the flues bare, it was stated by the captain, that 
the guage cocks had been tried, but on examining the boiler 
it was found that they were situated on the side of the 
boiler nearest the landing, and it is well known that on such 
occasions, the influx of passengers to that side is often so 
great as to change the level of the boat so much as to 
render the guage cocks, when so situated, useless. 

It is also possible, that the fireman who was by no means 
skilful, may have mistaken water of condensation in the 
tube, for that coming from the boiler. This last mistake 
is one that ought to be carefully guarded against, by leav- 
ing the cock open several seconds. 

Of the intense heat that steam sometimes attains, even 
without causing explosion, the following instance may be 
cited : the packing of the piston of a steam-boat, working 
with steam of a tension no greater than an atmosphere and 
a half, burst into flame on opening the cylinder, at least 
half an hour after the fire had been extinguished. Here it 
is evident, that any mixture of heated water with this steam 
might have caused explosion. 

Boilers, when the fire is made within, or when the return 
flues pass through them, are obviously far more subject to 
accidents arising from this cause, than those heated from 
without ; low pressure boilers are as liable to them as high, 
and it is confidently believed that very many explosions are 
to be attributed to this cause, against which the usual 
safety apparatus furnishes no protection. To pay the 
greatest attention to keeping the feeding apparatus in order, 
and to have the means of ascertaining at every moment 
the height of the water in the boiler, are the surest means 
of defence, but as the first of these may fail and does not 
act in many boilers after the engine is stopped ; and as the 
second depends upon the faithfulness of the engineer, or 



BOILERS. 99 

may also be clogged, and cease to give true indications ; 
other means have been proposed. 

53. The first of these is a thermometer, inserted through 
a collar into the part of the boiler occupied by the steam, 
and vrhich will therefore indicate its temperature. It must 
be made to mark the higher temperatures only, and may be 
graduated by a standard instrument, in a bath of hot oil. 
This is, however, but a fragile instrument, and may also be 
neglected by the workmen. 

64. Another method which promises to be effectual in 
many cases, is to form a part of the boiler of a plate of 
metal fusible at a comparatively low temperature. Such 
is an alloy of bismuth, lead, and tin, by varying the propor- 
tions of which a considerable difference in fusibility may 
be attained. They ought to be of such a mixture as not 
to melt, until heated beyond the temperature assumed as 
the limit of the heat to which it is ever desired to raise the 
steam, but fusible at one considerably below that at which 
the boiler becomes red hot. From 20*^ to 40** above the 
maximum heat the steam is meant to attain, will be well 
suited to the purpose, for they will then melt before any 
part of the boiler can become red hot. These plates must 
be adapted to the upper part of the boiler, and be of course 
in contact with the steam ; they are inserted at the end of 
tubes fitted steam-tight to the boiler. As they are apt to 
soften long before they melt, they ought to be covered by a 
diaphragm of wire gauze. When thus protected, they 
have been found not to give way until they actually melt. 
As different parts of the boiler may acquire different tem- 
peratures, two such plates will be needed upon its outer 
surface, at the two ends ; they ought to be as near to the 
body of the boiler as possible. When flues pass through 



100 BOILERS. 

the boiler we conceive that it would be a proper precau- 
tion to furnish them also with plates, of this description, 
but in this case, the metal might be less fusible, and lead 
unalloyed would suffice. 

When fusible plates are not used, and when from a 
thermometer, or from other appearances there is reason to 
apprehend that the water has fallen too low in the boiler, 
and that the temperature of parts of it have been raised 
to a dangerous degree of heat, the only means of safety, 
are to check the draught of the chimney by the damper, 
to lessen or extinguish the fire as soon as possible ; or even 
to procure rapid cooling by pouring water on the surface 
of the boiler. A damper kept open by the action of the 
engine, and closing the instant it stops, would have a good 
effect, and might be easily adapted to a centrifugual ap- 
paratus. 

55. It has been proposed, as a mode of securing Bafety in 
cases of great increases of temperature in the upper part 
of the boiler, to provide safety valves that would open at 
the limit of temperature beyond which danger might ensue. 
A safety valve of the usual form, but loaded with a great 
weight, and placed upon a tube containing a cylinder of 
metal, will answer this object ; let the metallic cylinder be 
supported from beneath, and of such a length that the 
dilatation by heat shall bring it in contact with the safety 
valve at the required temperature ; any further increase of 
temperature will open the safety valve, and permit the es- 
cape of the steam ; its action is certain, for the expansive 
force of the metals when heated is capable of overcoming 
the most powerful resistances : but it is rather to be used 
as an indicator of the necessity of moderating the fire, and 
putting the feeding apparatus in order, than as affording 
perfect security from explosion. 



BOILERS* 101 

It is in truth difficult to point out methods that are of 
themselves entirely to be relied upon to prevent explosions. 
However perfectly a boiler may be constructed or furnished 
with safety apparatus, it will still depend much upon the 
carefulness and intelligence of the persons entrusted with 
its management. One thing, however, appears certain, 
although contrary to general behef, that as the most usual 
causes of explosion affect low pressure boilers equally with 
those which generate high steam, the latter are not more 
subject to accidents than the former. There are precau- 
tions, however, which, if resorted to, may diminish the risk 
of such accidents in a very great degree ; so far, indeed, 
that without the greatest carelessness, they cannot occur. 
These may, perhaps, be recapitulated to advantage. 

1. Cylindrical boilers, without any return flue, either 
without or within, are safer than any others. 

2. Internal flues should be avoided wherever it is possi- 
ble, and especially the chimney, or vertical flue, should 
never be permitted to pass through the boiler. 

3. Every boiler should be furnished, in addition to the 
usual safety valve, with one not under the control of the 
fireman. 

4. All boilers should be furnished with guage cocks, or 
other apparatus, to shew the level of the water, and these 
should be so placed in steam boats, that no error in their 
indication can take place when the vessel heels or rolls. 

5. Plates of fusible metal should be provided, of a compo- 
sition melting so far above the usual temperature of the 
water and vapour, that they will not open on any ordinary 
occasion, but will give way before they attain a temperature 
that can be dangerous. 

6. A thermometer should be introduced into the boiler, 
whose indications may be seen from without. 



102 BOILERS. 

7. Self-acting feeding apparatus should be adapted to 
the boiler, by which water will enter and keep the fluid 
within at a constant level, and this should depend upon the 
waste of water and not on the action of the engine. It 
unluckily happens that no such apparatus has yet been 
contrived for high pressure engines, nor indeed for any 
where the tension of the steam exceeds li atmospheres. 
Neither are they always applied even to low pressure 
engines. 

8. The chimney should be provided with a damper by 
which the draught of the flues may be suddenly checked, 
and doors should, if possible, be placed upon the ashpit. A 
damper that would close as soon as the engine ceased to 
move, would be of great service in lessening the liability to 
explosion, and this does not appear to be difficult of attain- 
ment. 

9. The proof of the boiler should be conducted with the 
greatest care, first with water, at a pressure five or six 
times as great as the boiler is intended to carry, and after- 
wards with steam of twice the proposed tension. The 
water proof should be repeated from time to time, and 
every part carefully examined to ascertain that all the 
safety apparatus is in working order. 

Few or none of these precautions are usual in our Amer- 
can steam-boats : The boilers, even if cylinders, have both 
internal flues and furnaces, and the vertical chimney fre- 
quently rises in the boiler ; there is never more than one 
safety valve ; plates of fusible metal are unknown ; the 
feeding apparatus is merely a forcing pump, which is turned 
on or thrown off* at the pleasure of the engineer, and which 
does not act at all at the time the engine is not in motion ; 
but a very few steam boats have dampers upon their flues ; 
and the proof is wholly a matter between the maker and 
proprietor, and for its proper performance the public have 



BOILERS. 103 

no guarantee. Thus of all the precautions that have been 
proposed in order to insure indemnity from explosion, but 
two are in use among our steam-boats ; namely, the safety 
valve and the guage cocks ; the former being still subject to 
the caprice of the persons employed, and the latter having 
an uncertainty in their indications, both when the boat in- 
clines to either side, and when they contain, as they most 
frequently will do, water of condensation. Need we won- 
der that explosions have become frequent, and that they 
have produced the most fatal consequences 1 

The means which are used are not certain to insure safe- 
ty, even where the care of the officers of the vessel, and of 
the persons employed about the engine, is unremitting, and 
directed by the utmost intelligence, and hence dangerous 
accidents occur without giving rise to blame, and thus di- 
minish a proper feeling of responsibility. On the other 
hand, were the list of precautions that we have given, to 
be completed by a self-acting feeding apparatus, indepen- 
dent of the action of the engine, for a high pressure boiler, 
we conceive that no accident could possibly happen where 
they are employed, except through the grossest carelessness 
and inattention. 

Should it appear that the feeding apparatus does not act 
to supply as much water as is evaporated, the damper 
should be closed, and the boiler even cooled by the gentle 
application of water from without ; but it will always be a 
sure source of danger to inject water in abundance, or even 
to open the safety valve after the water has once fallen 
below its proper level, and before it is ascertained that nei- 
ther the temperature of the steam within, or of the sides of 
the boiler, are such as to cause a sudden conversion of the 
water that comes into contact with them into steam. 



W4 BOILERS. 

56. There is another species of danger which arises 
from the deposit of solid substances. Almost every kind 
of water that is used for boilers, contains more or less 
earthy and saline matter. The constant evaporation is 
replaced by new supplies of the same impure water, and 
the soluble portion or mechanical impurity is consequently 
accumulating. The soluble parts become greater in quan- 
tity than the contained water can hold in solution, and these 
deposited, along with those that are merely suspended. 
Crusts thus form on the lower part of the boiler, and the 
surface covered by them, being no longer in contact with the 
water, may be heated red hot, and may be corroded in con- 
sequence of the property that some of these salts have, of 
being decomposed by the metals at a red heat. The boiler 
will become weak in these places and be liable to burst. It 
hence becomes necessary to cleanse the boilers frequently ; 
for this purpose, as well as for examining the interior, an 
opening is made in the boiler, large enough to admit a man. 
This has a cover, which, when the boiler is in use, is fast- 
ened down by screw bolts and nuts, and is packed in such 
a manner as to be steam-tight. This opening is called the 
Man-hole. 

These deposits become more frequent and copious when 
sea-water is used, and it has been found necessary, in 
consequence, to cleanse the boilers of steam-boats that 
navigate salt water, at least once a week. 

When the water is fresh, and the deposit principally 
consists of sulphate of lime, as is the case with hard pump 
waters, vegetable feculse will suspend the impurities. To 
furnish this, potatoes may be thrown into the boiler, in the 
proportion of half the weight of bituminous coal that is con- 
sumed per hour. This quantity of that root once added, 
furnishes starch enough to keep the earthy matter suspend- 
ed by the water, for a long space of time, and it has not 



BOILERS. 105 

been found necessary to cleanse boilers when this addition 
is used, oftener than once a month. It is not known 
whether the same method will be effectual in preventing 
the saline deposits of sea water. 

57. It merely remains that we should speak of the pipes 
by which the steam is conveyed from the boiler to the 
engine. The size of these will depend on the quantity of 
steam the boiler is intended to furnish, the resistance the 
pipe itself opposes to the passage of the steam, and the loss 
of heat. 

Steam issues into a space containing atmospheric air 
with the velocities given in the table on p. 87. The veloci- 
ties with which it rushes into a vacuum are as follows, viz. 

Table of the Velocities with which Steam flows into a Vacuum. 



r 

Force of S 

I 

2 


team. 

Atmosphere, 
do. 


- 


- 


- 


■ ■■ 1 

Velocity per second. 

- 1908 

- 1977 


3 




do. 


- 


- 


~ 


- 2006 


4 




do. 


- 


- 


. 


- 2022 


5 




do. 


- 


> 


- 


- 2038 


10 




do. 


. 


. 


- 


- 2098 


15 




do. 


. 


- 


- 


- 2121 


20 




do. 


- 


- 


- 


- 2141 

















It will be seen from this table that the velocity of effluent 
steam increases very slowly with increase of temperature. 
This grows out of the fact that the density of vapour in- 
creases under ordinary circumstances, nearly as fast as its 
elastic force. Did both follow the same law, the velocity 
would not increase at all ; but the weight of steam expend- 
ed by a given orifice, increases rapidly, for the density of 

14 



106 BOILERS. 

hot steam is much greater, and the weight that passes out 
is in the compound ratio of the density and the velocity. 

The table on page 87 gives the velocity for high pres- 
sure engines, for they, as we shall see hereafter, are re- 
sisted by the pressure of the atmosphere. The table just 
given contains the velocities for condensing engines. Both 
of these, however, require a correction for the friction, and 
the loss of motion by cooling, but for these it is impossible 
to give any general rule. A method that has been found 
to succeed in practice is, to make the orifice, or nozzle, by 
which the pipe communicates with the engine, such as 
would be calculated from the velocities of the tables, and 
to make the rest of the pipe larger. The greater the dis- 
tance the steam has to pass, the larger should be the pipe, 
and to prevent the loss of heat growing out of the increa- 
sed surface, the metal should be kept bright, in which state 
it will be a bad radiator of heat. 

The principles for calculating the area of the orifice by 
which such pipes communicate with the engine, and the 
surfaces of safety valves are therefore identical, we shall, 
in order to render them more intelligible, reduce them to 
the form of a Rule. 

To find the area of the passage by which steam shall 
reach the engine from the boiler in which it is generated : 

Divide the quantity of water in cubic inches evaporated per 

hour, by 3600, (the number of seconds in an hour,) multiply 

the quotient by the volume of steam of the given temperature, 

from the table on page 35 : This will give the number of cubic 

inches of steam that must pass per second. Divide this by the 

velocity per second, taken in the cases of high steam pipes, 

from the table on page 87, and in the case of low steam pipes 

from the table on page 105. The quotient is three-fourths of 

the required area, whence the diameter of the circular section 

can be obtained in the usual manner. 



BOILERS. 107 

A very beautiful and ingenious boiler, to be heated by- 
anthracite coal, has recently been adapted to a locomotive 
engine by Col. Miller, of Charleston, S. C. The boiler is 
a cylinder, placed in a vertical position, and terminated by 
a truncated cone. The fireplace is an inner concentric 
cyhnder, terminated at top in a dome. Through this, pipes 
pass, to convey the current of heated air that has passed 
through the furnace, and these unite in a single chimney, to 
which the upper edge of the truncated cone, that forms the 
upper part of the boiler, is rivetted. To increase the fire- 
surface, tubes, with hemispheric bases, descend from the 
dome into the furnace. This boiler has been found, by ac- 
tual experiment, to generate more steam with an equal 
quantity of the fuel, than any other to which that species of 
combustible has been applied. We deem it due to justice 
to state, that Mr. John Stevens, of Hoboken, communi- 
cated to us, some years since, a plan of a boiler on similar 
principles, that we do not doubt would have been equally 
efficacious, but the actual execution by Col. Miller was 
made without any knowledge of the plan of Stevens. 

58. Besides boilers of the kinds we have mentioned, Mr. 
Perkins has recently proposed one upon very different 
principles, which, for the sake of distinction, is called a 
Generator. It is a strong vessel, completely filled with 
water, which is heated to a very high temperature, and 
prevented from being converted into steam by the strength 
of the vessel and the pressure upon its safety valve. A 
small quantity of water is flashed in from a forcing pump, 
which causes the escape of an equal quantity, that is 
instantly converted into steam of high temperature and 
consequent elasticity. As it is our intention to confine 
ourselves to forms that have actually come into general 
use, and as the generator of Perkins is still a subject of ex- 



108 BOILERS. 

periment, it does not enter into our views to describe it 
more particularly. 

On Plate I. will be seen various forms of boilers. 

Fig. 1 and 2, are a longitudinal section and front eleva- 
tion of the low pressure boiler of Watt, together with its 
furnace. 

aa a a, body of the boiler. 

b, furnace, with its grate, c, ashpit. 

d d d, flues. 

e, man hole, for entering the boiler to cleanse it. 

/, steam pipe, g, steam guage of the form shewn on a 
larger scale at Fig. 7. 

h, safety valve of the form shewn at Fig. 12. 

i, float of the feeding apparatus. 

k k, lever of the feeding apparatus, I, valve of the feed- 
ing apparatus. 

m, supply cistern fed by the hot water pump of the engine, 
below this is the tube that conveys the water to the boiler, 
and which contains the float n of the self-acting damper. 

0, pullies of the self-acting damper p, 

q, feed pipe. 

r r, guage cocks. 

Pig. 3. is a transverse section of a cylindrical boiler, 
the same letters are employed to designate such of the 
parts as are represented. When used for low steam all the 
parts represented in the preceding figures, may be applied 
with equal facility to it. The faint circle within, shews 
how the return flue might be made to pass through this 
boiler. 

Fig. 4, is a cyUndrical boiler with internal furnace and 
flues. 

On PI. VII. may be seen an outside view of a low pressure 
boiler for a steani-boat ; this has an interior furnace and 
flues. 



BOILERS. 109 

On PI. VIII. is a plan and section of an English steam- 
boat boiler. 

On PI. VI. are end views of a pair of cylindrical boilers 
for a high pressure engine ; and on PI. IX. a cylindrical 
boiler for a locomotive engine. 

This last is, however, objectionable on account of the 
great weight of water that it contains, and its want of 
strength. 

Having thus explained the structure of the boiler, and 
of the various accessaries with which it may be furnished, 
in order to render its action more regular and safe, we shall 
next proceed to treat of the action of steam as a mover of 
machinery, and of the different forms of engine that are at 
present in use. 



CHAPTER IV. 

GENERAL VIEW OP THE DOUBLE-ACTING CONDENSING 

ENGINE. 

Of Prime Movers in general. — Principles of the action of Ma^ 
chines. — Modes of applying Steam as a prime mover, — 
•Application of Steam to the Double-Acting Condensing 
Engine. — Modes of removing Water of Condensation and 
Vapour. — Modes of changing the reciprocating Retilinieal 
Motion of the Piston Rod into a reciprocating circular mo- 
tion. — Method of changing the reciprocating circular motion 
into a continuous one. — Mode of regulating the varying mo- 
tion of the Engine and making it produce one with uniform 
velocity. — Other methods of obtaining a rotary motion. — 
Effect of the joint action of two Engines. — Water used to 
produce condensation. — Water that has been employed in 
condensation applied to feed the boiler. — Manner of ascer- 
taining the state of the Vacuum formed by condensation. — 
Mode of regulating the supply of Steam. — Accumulation of 
Steam in the boiler, and rdode of preventing it. — Double- 
acting condensing Engine considered as self-acting. — 
Packing and Cements .—Estimate of the power of the double- 
acting Condensing Engine. — Estimate of the quantity of 
water evaporated for each unit of force. — Estimate of the 
supply of water for the boiler, 

59. The agents which we employ for the production of 
mechanical effects through the intervention of machines^ 
may be divided into three classes. 



112 DOUBLE-ACTING 

1 . The muscular force of man and living animals ; 

2. The force of gravity producing the descent of heavy 
bodies, whether solid or fluid ; 

3. Heat, applied either to change the volume of bodies 
that do not change their mechanical state during its action, 
or to convert bodies into elastic fluids, acting with a power- 
ful expansive force. 

To the second of these classes, we refer the force of 
running water, descending in channels to find the lowest 
accessible level ; to the third, the currents of the atmos- 
phere or wind ; and the more powerful agency of inflamed 
gunpowder, and of liquids converted into steam. 

60. Machines are instruments by which we change the 
direction or intensity of the moving force. They can all be 
reduced to six simple forms, called Mechanic powers, and 
these again to two still more simple modifications. In their 
action there is but one principle involved, which is as fol- 
lows : The product of the moving force, estimated in some 
conventional unit, into the space through which the point to 
ichich this force is applied, is, in all cases, equal to the sum 
of the products of all the resistances into the spaces described 
by their respective points of application. 

This principle has two distinct cases ; in the first, the 
machine is at rest, or in equilibrio, under the action of the 
power and the resistances. In this case, the points of ap- 
plication must be supposed to move, and the space em- 
ployed in the calculation is that through which they would 
move, without altering the conditions of equilibrium. The 
principle is, in this case, called that of Virtual Velocities. 
In the second case, the machine moves with uniform velo- 
city under the action of the opposing forces, and is said to 
have attained a state of permanent working, or to be in 
dynamical equilibrium. 



CONDENSING ENGINE, 113 

A machine passes from the state of rest, in consequence 
of the condition we have stated being violated, and the 
moving power acquiring a preponderance over the resist- 
ances. It leaves the state of rest gradually', and therefore 
moves at first with accelerated velocity, the condition we 
have stated, so long as this acceleration is going on, no 
longer holds good, and there is one case in which the ac- 
celeration might continue as long as the motion. This is 
when a force is capable of acting with equal intensity upon 
a body at rest and upon a body in motion. Of the three 
classes of forces we have mentioned, gravity is the only one 
that thus acts, and it is limited by the check that the mo- 
tion meets, iii consequence of the body acted upon reaching 
the solid mass of the earth, the resistance of which speedi- 
ly brings it to rest. But even in the case of this force, the 
bodies that are propelled by it meet with resistances, that 
may finally render their motion uniform. Thus a stream of 
water, although propelled by the force of gravitation, moves 
in a pipe or channel of constant section, with uniform ve- 
locity. In all other cases, the action of the moving for<;e 
does not depend upon the velocity with which the body in 
which it resides moves, or has a tendency to move, but 
upon the difference between this and the velocity of the 
machine to which it is applied. Hence, when the point of 
application is at rest, the force acts upon it with the whole 
intensity it is capable of exerting, but when this point has 
a velocity equal to that of the body through which the force 
acts, the former no longer receives any impulse from the 
latter. As then the motion grows out of the superiority of 
the moving force, and as the action of this force diminishes 
with every increase of velocity of the point to which it is 
applied, equihbrium between its action, and that of the re- 
sistances must again take place, and if they both act upon 
a machine it will assume a state of permanent working. 

15 



114 DOUBLE-ACTING 

We have used the term resistance, for the machine must 
not only do the work for which it is constructed, but must 
also overcome retarding forces that exist in the very nature 
of materials and workmanship, or which grow out of ex- 
trinsic causes. Friction is the retarding force from which 
no material is free, and which no perfection of workman- 
ship can wholly remove ; the more important of extrinsic 
forces is the resistance of the fluids, in which machines 
may be placed, and which in most cases is that of the air 
of the atmosphere. 

We measure the mechanical action of a force not merely 
by the weight it is capable of raising, but by the space 
through which it raises that weight in given time. Hence, 
as the product of the moving and resisting forces, into the 
respective spaces through which their points of application 
pass, are equal either in the states of ordinary or dynami- 
cal equiUbrium, the measure of these forces is also equal, 
and even were there neither friction nor resistance from the 
air, the utmost work a moving force is capable of performing 
is no more than its own measure. Thus nothing is gained 
by any machine, if considered abstractly, while the whole 
amount of friction and the resistance of the air is absolute 
loss. 

In practice, however, machines are of very great value, 
in spite of this actual waste of moving power : we are 
enabled by them to accommodate the direction of the mo- 
tion of the agent employed, to that of the work to be per- 
formed ; we can render a power that has a fixed and de- 
terminate velocity, capable of douig work with any other 
given velocity ; we can apply a natural agent, whose inten- 
sity is determinate and invariable, to overcome a resistance 
of far greater intensity, although at the expense of a loss 
of velocity ; and we can in either or all of these cases, 
bring to the aid of the power of man, the action of the 
great natural agents, water, wind, and steam. Thus, then^ 



CONDENSING ENGINE. 115 

tbe exertion that man must apply, when furnished with 
proper machines, to enable him to make use of these great 
agents, may frequently become wholly intellectual, and he 
will no longer have need of his mere physical energies; 
or at any rate, a single man will be able to direct the action 
of a power to perform a work, for which the united strength 
of thousands would be insufficient. 

It is in the appHcation of steam to machinery, that this 
triumph of human mind, over matter and the elements, is 
most remarkable. 

61. Steam may be applied as a moving power in three 
different modes : it may act against a space devoid of air, 
in this case, if proceeding from a water of the temperature 
of 212% it exerts a force equivalent to the pressure of the 
atmosphere ; or, if heated to a higher degree in a close 
vessel, with a force corresponding to the increased temper- 
ature, according to the law stated on page^34; it may be 
admitted, at high temperature, into a space greater than it 
is capable of filling, at the density that corresponds to its 
heat, and act against a space void of air by its expansive 
force ; or, it may, if proceeding from water heated to a high 
degree, in a close vessel, be able not merely to overcome 
the resistance of the atmosphere, but to exert, in addition, 
a great mechanical force. 

In the two first cases, it is necessary to have the means 
to form and keep up a vacuum. The mode universally 
employed for this purpose, consists in taking advantage of 
the condensation of steam itself into a liquid form. By the 
table upon page 35 it appears that the volume of steam at 
the temperature of 212'' is 1696 times as great as that of 
the water whence it is generated ; hence, its complete con- 
densation would leave but y ^V^ of the space it previously 
occupied, filled with any material substance. Such com- 



116 DOUBLE-ACTING 

plete condensation is indeed impossible, for reasons we shall 
hereafter refer to, but it is yet obvious, that a vacuum of a 
considerable degree of perfection may be thus attained. 

The condensation of steam is effected by withdrawing 
its latent heat, this is done in the steam engine by the appli- 
cation of cold water, that may either be applied to the sur- 
face of the vessels, that contain it, or actually brought 
into contact with the steam itself. In the method now 
universally adopted into practice, the vessel is not only kept 
cool by immersion in a cistern of water, but a jet of cold 
water is constantly flowing into it. 

62. Let a piston be fitted steam tight to a cylinder, closed 
at each end, and let the space both above and below it be 
filled with steam ; if the steam beneath the piston be sud- 
denly condensed, and fresh steam be permitted to flow into 
the upper part, the piston will be depressed to the bottom of 
the cylinder by the whole energy of the steam, as given 
in the table on page 34 ; if, so soon as the piston has 
reached this lowest position, steam be admitted beneath it, 
and the steam resting upon the upper side be suddenly con- 
densed, the piston will now be forced upwards with a force 
equal to that, by which it w^as caused to descend ; on reach- 
ing the top the piston may again be forced down, and this 
alternating action may be bept up as long as steam can be 
supplied on the one hand, and the means of condensing it 
found upon the other. 

If now a rod be passed through a collar in one of the 
lids of the cylinder, and fastened at one of the ends to the 
piston, this rod may be made the means of conveying the 
force, that the steam exerts upon the piston, both in its 
ascent and descent, either directly, or through the inter- 
vention of other bodies, to some point at which it may be 



CONDENSING ENGINE. 117 

made to perform some regular work, or overcome some 
resistance. 

63. If the steam be condensed within the cylinder, there 
will be a great loss of heat, and consequent increase in the 
expense of supplying the moving power. Whether this 
condensation be effected by affusion of water upon the 
outer surface of the cylinder, or by the injection of a stream 
into its interior, the temperature of the enclosed space and 
of the sides of the vessel will be lowered, and the heat the 
steam has communicated to them, wholly or partially with- 
drawn. When the motion of the piston is to be reversed, 
and steam begins to enter on the side on which it was before 
condensed, it must again heat the piston and the adjacent 
parts of the cylinder, up to its own temperature ; this it 
does by parting with its latent heat, and it is consequently 
condensed ; the steam flowing from the boiler, therefore, 
exerts no mechanical action, until the heat, before abstract- 
ed, is again replaced ; as the piston moves, fresh portions of 
cooled surface are exposed, and fresh quantities of steam 
must be expended in heating them. Such is the effect pro- 
duced by the alternate heating and cooling of the parts, that 
it has been found, by actual experiment, that at least five 
times as much steam is expended upon them, as is necessary 
simply to fill the cylinder. 

Hence, it is obvious, that the steam ought to be con- 
densed in a separate vessel, having a communication alter- 
nately with the upper and lower sides of the piston. 

64. Water is capable of forming vapour at all tempera- 
tures whatsoever. Its tendency to rise is, however, imped- 
ed by pressure, and thus it does not boil in an open vessel, 
when the rising of steam is impeded by the resistance of 
the atmosphere, until it reach the temperature of 212". 



118 DOUBLE-ACTING 

But with each diminution of pressure, the boiling tempe- 
rature becomes lower, until, in the vacuum of an air pump, 
it boils at 90*^ : Hence, so soon as a portion of the steam 
is condensed, fresh vapour will be rapidly formed, at a 
lower temperature, and although the expansive force of 
this diminishes in a geometric ratio, yet it is still capable 
of opposing a resistance to the motion of the piston. 
This resistance is such that it has been found by experi- 
ence, that the vapour of water of 212% whose expansive 
force is equivalent to a pressure of 151bs. on every square 
inch, had never acted upon the piston with a mean force of 
more than lOlbs. until means were applied to remove or 
obviate this resistance. 

It may be removed, or at least very much lessened, by 
taking care to keep up a vacuum in the separate conden- 
ser. Two modes present themselves for doing this : the 
engine may be placed at least 34 feet above the level of a 
cistern of water, and the condenser may be made to com- 
municate with it by a pipe. As that height is the maxi- 
mum distance to which the pressure of the atmosphere 
can raise a column of water, the water of condensation 
and the condensed steam will flow into the pipe, and as 
much will pass out at its lower end ; the water being sup- 
ported at a constant level by this pressure. It, however, 
happens so rarely that a proper situation can be found to 
carry this plan into effect, that it has never been applied to 
practice, and has ceased even to be thought of by those 
concerned in the construction of steam engines. 

A pump has therefore been resorted to, in order to keep 
up a vacuum in the condenser by carrying, off the water of 
condensation, and the vapour that may remain, or be again 
generated. This pump is called the Air Pump. It is, with 
the condenser, immersed in a cistern of cold water, and a 
jet of that fluid plays through an aperture into the con- 



CONDENSING ENGINE. 119 

« 
denser. In this manner a greater cooling surface is brought 
into contact with the steam, and the condensation is effect- 
ed more rapidly than could be done, by simply cooling the 
surface of the condenser. The water that thus enters is 
regulated to the working of the engine by a valve called 
the Injection Cock. 

65. The alternating rectilineal motion of the piston' in 
the Cylinder of the engine, can of course be only directly 
applied, to perform a work with the same species of motion, 
and with equal velocity. Thus, by passing the piston-rod 
through the bottom of the Cylinder it might be made to 
work a pump, or by laying it in a horizontal position, to 
drive a horizontal blowing machine. But the cases, where 
this direct application is possible, are very few and unim- 
portant, and they have never been introduced into prac- 
tice. Even where a motion of the same kind, and with 
equal velocity is required, it is the more usual custom to 
carry the motion of the piston-rod to the place where the 
work is to be performed, through the intervention of a I 
Balance or Lever beam, resting upon pivots. 

This beam, having the axis that passes through these 
pivots fixed, its ends move in circular arcs with reciprocat- 
ing motion. Now as the motion of the piston-rod, although 
reciprocating, is rectilinear, it becomes necessary to make 
the connexion between the piston-rod and the beam, of 
such a nature as will permit the one of these motions to be 
accommodated to the other. 

The simplest, and it might almost be said the most obvi- 
ous plan, is to affix a bar to the end of the piston-rod, at 
right angles to its direction, and make the ends of this bar 
describe straight lines, by adapting them to straight guides 
of iron ; the end of the piston-rod being thus kept to its 
rectilineal course, the end of the beam is attached to it by 



120 DOUBLE-ACTING 

a bar, that has a motion upon cylindrical gudgeons, affixed 
both to the piston-rod and the beam. Through this bar 
the force that impels the rod in its ascent and descent is 
conveyed to the beam, and the gudgeons allow the bar to 
change its position in such a way, that one end may always 
move in a straight line, and the opposite one in an arc of 
a circle. 

We have said that this method would seem the most 
obvious ; it is, however, of but very recent introduction, 
and has indeed been but little used, even up to the present 
moment. Instead of it, and in order to produce a similar 
effect, an apparatus, called the Parallel Motion is employed. 
A similar bar connects the piston-rod to the end of the 
beam, but the former has no guides ; a parallelogram is 
then formed of this rod, of a part of the lever-beam and 
of two bars equal and parallel to them ; the two gudgeons 
we have mentioned, are situated at two of the angles of 
this parallelogram, and at the other angles the connexion 
between the pieces that form the sides, is also effected by 
gudgeons or pivots. This parallelogram has therefore 
sides of a constant magnitude, but the angles are capable 
of variation in size, by the motion of the sides upon the 
pivots that connect them. The pivot, at the angle, diago- 
nally opposite to that where the end of the beam is joined 
to the bar, that connects it to the piston-rod, is attached by 
a bar to an immovable pivot in the frame of the instru- 
ment, or in an adjoining wall. By this last connexion, the 
point at this last named angle, will, when the beam oscillates, 
describe a circle around the centre of the fixed pivot. 

The points, at the two angles of the parallelogram, that 
are situated at the end of, and upon the beam, will also 
describe circular arcs, whose convexity is turned towards a 
direction, opposed to that described by the point attached 
to the fixed pivot. When the radii of these three different 



CONDENSING ENGINE. 121 

arcs bear a proper relation to each other, the remainmg 
angular point of the parallelogram will describe a straight 
line. Its path is in truth a portion of a curve of contrary- 
flexure, but, within the limits of the oscillations of the 
beam, it does not differ sensibly from a straight line. But 
as it is not really and truly a straight line, this method, 
however ingenious, is both less perfect in theory, and more 
complex in practice than the other. The side of the paral- 
lelogram, that forms the parallel motion, opposite to that 
which is a part of the working beam, is called the Parallel 
Bar ; the remaining two sides are called Straps ; the bar 
which connects the lower angle of the parallelogram, to 
which the piston-rod is not fastened, with a fixed pivot, is 
called the Radius Bar. 

We have spoken of the bars, that, with a part of the 
beam, make up the parallel motion, as single. So far as 
there theory is concerned, this is sufficient, but for the 
sake of a proper adjustment of the pivots, the straps are 
made double. 

In the pair of straps nearest the fulcrum of the lever 
beam, there is another parallel motion, which is applied to 
work the air pump. It consists in adapting a pivot, to the 
two straps to which the pump-rod is attached, by a circular 
socket, in such a way that the direction of the rod is not 
changed by the motion of the pivot ; this pivot, thus placed, 
between two points which describe circular arcs, convex 
towards opposite directions, may be so adjusted in its dis- 
tance from each respectively, as constantly to describe a 
straight hne. The principle of these parallel motions will 



16 



123 DOUBLE-ACTING 

be understood by reference to the following description 
and figure. 

m 6 is a part of the lever beam in its lowest position, m be 
ing the centre on which it vibrates ; to the points a and 6 arc 
attached the straps a f c and h d, and to these the paral- 
lel bar c d, the axis of the parallel bar is in a line passing 
through b, and its other end is attached to the point c. The 
four angles abed are formed by pivots so as to have a 
free motion, and the radius bar has pivots both at b and c* 
Thus the points a and b will, when the beam moves, des- 
cribe the circular arcs a g i, and b I k, while the point 
c will describe the circular arc c e f, whose convexity is 
opposite to the two former arcs ; and they will compel 
the point d to describe the straight line d b h. In this 
figure the line a b is half the length of one arm of the 
lever beam, and the radius bar is equal to the same line, 
but there may be other proportions; all that is necessary, is 
that the radius bar shall be equal in length, between its 
centres, to the distance between the points m and a. 

The second parallel motion is formed by placing a pivot 
/, at the point where the line m d cuts the side a c of 
the parallelogram, this point will then be compelled to des- 
cribe the straight line fan. 

For the parallel motion has recently been substituted the 
following arrangement, to which we have already referred 
as still simpler. To the end of the piston-rod is attached a 
bar, or cross head, at right angles to it, the ends of this are 
placed between parallel vertical guides, situated in the plane 
passing through the line d b h. The cross beam is turned, 
at two places, into the form of pivots, to which the straps, 
that unite the piston-rod to the working beam, are applied. 



CONDENSING ENGINE, 



123 



PARALLEL MOTION. 








•^^N 



124 DOUBLE-ACTING 

66. The end of the beam, opposite to that which is at- 
tached to the piston-rod, has also a reciprocating circular 
motion, rising as the other end falls, and falling as it rises. 
This species of motion is hardly adapted to be appUed 
directly to any usual species of work. In most of the im- 
portant applications of the steam engine, the required 
motion is circular and continuous. It hence becomes 
necessary to convert the reciprocating motion of the work- 
ing end of the beam, into the last named variety of motion* 
This change is eiFected by the intervention of the Connect- 
ing Rod, or shackle bar, and the Crank* 

The connecting rod is a bar of iron attached to the 
working end of the lever beam by a cylindrical pivot, and 
a circular socket, in which it has a free motion. The 
crank is an arm or radius of iron, having a pivot at each 
end, one of these is fixed in a horizontal position to a socket 
in a sohd support, and the arm has a free motion around 
the axis of this pivot ; the pivot at the other end projects 
from the arm, and is inserted in a socket on the lower end 
of the connecting rod. The length of the crank between 
the axes of the two pivots, is equal to the space passed 
through by the piston in the Cylinder, or what is called the 
length of the stroke. It is at least so, when the arms of 
the beam are of equal lengths, as is most usually the case, 
and when they are not, this distance has the same ratio to 
the length of stroke as the arms of the beam, to which the 
connecting rod and piston are respectively attached, have 
to each other. The working end of the beam, rising and 
falling in a circular arc, under the impulse conveyed from 
the Cylinder through the parallel motion, will act upon the 
crank through the intervention of the connecting rod ; the 
moveable end of the crank will describe, under this influ* 
ence, a semicircle during the time that the beam either rises 
or descends : this semicircle may be directed to either side 



' CONDENSING ENGINE. 125 

of the vertical line passing through the axis of the crank ; 
and a slight force applied to it in a proper direction, at its 
highest or lowest positions, will cause it to describe a com- 
plete circle. 

This apparatus may be better understood by reference 
to Fig. 5, on PL IV, where ^ represents the end of the 
lever beam, b the part of the connecting rod, which is 
forked at the end, and embraces the beam ; c, the connect- 
ing rod represented in its highest position ; d, the pivot on 
the crank to which the connecting rod is attached ; E, the 
arm of the crank of which/ is the centre ; g, h, i, k, repre- 
sents four other positions of the crank. 

67. The force that renders the rotary motion of the 
crank continuous, is derived from the fly-wheel, which also 
fulfils another most important purpose. 

No motion can well be imagined more irregular than that , 
of the piston of a steam Cylinder. When it is in contact 
with either end of the Cylinder, the entrance of the steam 
gradually impels it from a state of rest, until it acquires a 
maximum of velocity, whose magnitude depends upon the 
relation between the supply of steam, and the work to be 
performed. When it reaches the opposite end of the cylin- 
der it again comes to rest, more or less suddenly, accord- 
ing to the manner in which the steam is supplied and cut 
oflf. A motion in the opposite direction next succeeds, 
gradually increasing at first, and again ceasing when the 
piston reaches the opposite limit of its motion. It will be 
thus seen, that not only is the direction of the motion alter- 
nating, but that its velocity is continually varying, and that 
at two instants there is no motion whatever. Now in very 
many applications of steam, it is not only necessary that 
the action be continuous and circular, but that its rate 
should be uniform. To eflfect these two objects, advantage 



w 



126 DOUBLE-ACTING 

is taken of the nature of matter, which has not the power 
either of setting itself in motion, or bringing itself to rest : 
hence, when a mass is once set in motion, it will have a 
tendency to move forward continually, and with uniform 
velocity ; this it will tend to do, although the force that 
set it in motion cease to act ; and if its motion be resisted, 
the moving mass will communicate motion to the bodies 
which oppose it. The part of a machine in which this 
principle is called into action, is called a Fly-WheeL It is 
usually a heavy circular ring, attached, by radiating arms, 
to the axis of a part of the machine that has a rapid motion. 
In steam engines it is fixed to the axis of the crank. The 
fly-wheel, like every other part of a machine, opposes a 
resistance to the moving power, and requires a certain ex- 
penditure of force to set it in motion ; but when once it is 
set in motion, it requires but small accessions of force, and 
these may be exerted at intervals, to keep it moving with 
the greatest mean velocity the moving power, acting 
through the intervention of the machine, is capable of 
communicating. If the power be variable, and therefore 
have a tendency to cause irregularity in the motion of the 
machine ; the fly-wheel resists acceleration, on the one 
hand, because it cannot suddenly acquire a new velocity, 
but will oppose any increase with a force equivalent to the 
product of its mass into the difference between the velocity 
it has, when the acceleration begins to act, and that which 
the accelerating force is capable of giving ; on the other 
hand, its motion cannot be suddenly checked, when the 
force is either lessened or ceases to act, it therefore goes 
on, with a velocity, decreasing only in consequence of the 
resistances it meets. In parting with its motion, it will 
communicate as much to the bodies that resist it, and 
will thus keep up the velocity of the machinery driven by 
the engine, and render that of the engine itself regular, 



CONDENSING ENGINE. 127 

until the acceleration again commences. Hence, in the 
varying action of the piston of a steam engine, the fly-wheel 
moderates the speed when it has a tendency to become 
greatest, receiving then an accession of force ; this it dis- 
tributes again among the parts of the machine that are in. 
motion, when the speed of the piston lessens, or actually 
becomes nought, which happens when it reaches its highest 
and lowest points. If the mass and velocity of the fly- 
wheel be made great, this tendency to uniformity will be- 
come absolute, and it will go on with uniform velocity, 
under the constant variation of the motion originally re- 
ceived from the prime mover, giving to the machinery 
driven by the steam engine, a regular and constant velocity. 
This tendency of the fly-wheel to go forward with con- 
tinuous rotary motion, accelerated at first, until it reach a 
mean between the maximum and minimum velocity the 
piston is capable of communicating to it, through the in- 
tervention of the parallel motion the working beam and the 
crank, is attained by its passing through a single semicircle, 
or by performing no more than half a revolution ; hence, 
when the piston reaches its upper or lower position, and 
the steam ceases for an instant to act, the fly-wheel carries 
the crank forward beyond the vertical line ; the new 
impulse derived from the steam, when it acts on the oppo- 
site side of the piston, is exerted to compel the crank to 
move forward, in the opposite half of the circle it before 
described, and therefore with continuous rotary motion. 

The form and mode of action of the crank has a very 
beneficial influence, in permitting the uniform motion of 
the fly to be attained without exerting any injurious action 
upon the engine itself. The force of the crank is always 
applied to the fly-wheel, in the direction of a tangent to the 
circle the crank itself describes ; the force of the steam acts 
upon the crank in the direction of the connecting rod. 



128 DOUBLE-ACTING 

When the force of the steam is nothing, in consequence 
of the piston being in the act of changing the direction of 
its motion, these two lines are at right angles to each 
other ; the crank may therefore be carried forward by the 
.fly-wheel, without being interrupted by the absolute cessa- 
tion and subsequent change in the direction of the motion 
of the piston. But when the steam is exerting its maxi- 
mum force upon the piston, these two lines nearly coincide, 
and the crank receives the whole force of the steam. 
Among all the modes, therefore, by which a variable and 
alternating motion is converted into one that is continuous, 
none is more advantageous than the crank, and few as much 
so. One, which will be mentioned in the history of the 
Steam Engine, has equally good properties in this respect, 
and we know of no other. 

Persons ignorant of the principles of mechanics, are in 
the habit of considering and declaring, that much power is 
lost when motion is conveyed through the intervention of 
a crank. This idea appears to have been originally found- 
ed upon what occurs, when a man works by means of a 
winch, an apparatus similar to a crank, and acting upon 
the same principles. Here a power, which, when con- 
stantly and directly exerted, is capable of balancing a 
pressure of 701bs., is not capable of overcoming a resist- 
ance of more than 251bs. This, however, arises from the 
force itself actually falling, during one part of the revolu- 
tion of a winch, as low as the last named limit, and hence 
the revolution cannot be completed, if the constant resist- 
ance exceed that amount. The power of a man depends 
not only upon his muscular force, but upon the manner 
and direction in which that muscular force is exerted, and 
in some parts of the motion of a winch, this manner is ex- 
tremely unfavourable. The crank or winch still acts upon 
the resistance, with the whole force the man applies to it. 



CONDENSING ENGINE. 129 

but this is less at some parts of the revolution than it is in 
others. In the steam engine, a similar variation in the in- 
tensity of the prime mover occurs, and it is greater in 
amount ; but while a man is as much, and even more fa- 
tigued in applying his force, in the unfavourable positions 
of the winch, the varying motion of the piston of the steam 
cylinder corresponds exactly with a variation in the expen-« 
diture of steam. 

As a general principle in mechanics, no force can be 
lost ; it may be applied to resistances which do not enter 
into the estimate of the work performed, for instance, to 
overcome the friction of the machine ; or it may, by im- 
proper or disadvantageous direction, be wasted upon the 
machine itself, whose parts it thus tends to tear asunder or 
wear away. This last circumstance does occur in the ac- 
tion of a steam engine, such as we have described it, but the 
crank is not the only part which is liable to this objection. 
The rod or strap, that forms a part of the parallel motion, 
does not always act in the direction of a tangent to the 
arc described by the end of the working beam, with which 
it is connected. Hence, it at times expends a part of the 
force of the engine upon the beam, tending to draw it from 
its place. A similar obliquity occurs where the connect- 
ing rod is attached to the opposite end of the beam, and 
a similar waste of power. In the crank, the connecting 
rod acts upon it at all angles with its tangent, from 0" to 
90 ** ; and hence a part of the force is wasted to draw the 
axle of the crank from its seat. Were the force of the 
steam constantly exerted upon a connecting rod three 
times as long as the stroke of the engine, the power thus 
wasted would bear to the whole power of the steam the 
proportion of 0.225 to 1, but as the steam actually ceases 
to exert any force at the upper and lower points of the 
crank's revolutioi^, here no loss can occur, and the waste 

17 



130 DOUBLE-ACTING 

cannot exceed the ratio of 0.139 to one, or about one- 
seventh part, while, if, as usually happens, the pressure of 
the steam first gradually increases, and then again dimin- 
ishes, the real waste need not exceed one-tenth part of 
the force of the engine. A longer connecting rod causes 
the power to act more directly, and its waste to be conse- 
quently less. 

This waste is far less than the friction of the engine, and 
still less than the increase the friction would acquire in 
any of the methods that have yet been proposed, or are 
perhaps possible, of making the steam act directly upon a 
body, so disposed as to be capable of acquiring a rotary 
motion, instead of applying it to a piston working with 
alternate strokes in a cylinder. We are therefore disposed 
to think that the various plans, that have been proposed 
of constructing rotary engines, have been a sheer waste of 
ingenuity, and that there is little hope of any, that may 
hereafter be constructed, equalling the double-acting cylin- 
der engine in the property of applying advantageously a 
given quantity of steam. 

68. The method we have described, of converting 
the alternating motion of the piston-rod to a contin- 
uous rotary one, through the intervention of a parallel 
motion, a working beam, a connecting rod, and a crank, 
is not universal. The change is sometimes effected more 
immediately, by affixing the connecting rod, to a cross- 
head on the end of the piston-rod, which is then made to 
work between guides. When the Cylinder is vertical, the 
connecting rod and crank are usually double, the former 
descending on each side of the Cylinder. We have seen 
more than one plan, in which the Cylinder itself was sus- 
pended upon trunnions, permitting it to have a vibratory 
motion. In this last form, the connecting rod may be dis- 



CONDENSING ENGINE. 131 

pensed with, and the piston-rod acts immediately upon the 
crank. The steam is admitted to the Cylinder through ^ 
the trunnions. Such was the condensing engine of French, 
placed in a boat on the Hudson river, in 1808, and such 
is the high pressure engine constructed recently by an 
ingenious workman in the employ of the West Point 
Foundry. This mode of suspension is, however, only 
suited to small engines, where the Cylinder has but little 
weight. When the beam is suppressed, there results 
a very considerable saving of room, and there are occa- 
sions where this is very important. An engine, that has no 
beam, will occupy a space, whose length is less than half 
that taken up by one that has. In many of the American 
steam-boats, and particularly in all constructed under the 
direction of Fulton, the engine has this form. In the 
Western States, it is usual, not only to suppress the beam, 
but to lay the cylinder in a horizontal position. This last 
method has many advantages, among which may be men- 
tioned as the principal, that a steam-boat is far less injured, 
by a force acting in the direction of its length, than by 
one exerted vertically, and that the engine may be laid 
entirely under deck, without interfering with any of its 
more valuable properties. 

On the other hand, the suppression of the working 
beam has this disadvantage, that the obliquity of the action 
of the piston upon the connecting rod, is greater than 
occurs when the parallel motion and beam are used, and 
that the loss growing out of this obliquity, is greatest in 
proportion to the power, when the latter is a maximum ; 
hence, the waste, compared with the mean power, is 
greater than in the other case. This, however, does not 
apply to Cylinders hanging upon trunnions, for, in them, 
the power is applied directly, when at its maximum of 
intensity. 



132 DOtJBLE-ACtiNG 

69. In some few cases, the motion communicated to the 
fly-wheel is rendered more uniform, by using two complete 
engines, whose cranks are adapted to the same axle, but 
are situated in planes at right angles to each other. When 
the piston of one of these Cylinders has reached the top or 
bottom, that of the other will be in the middle of its 
stroke. One of them will therefore be acting at its maxi- 
mum of force, when the other ceases to act altogether. 
This plan is far preferable in effect to that of a single en* 
gine of the same nominal power, but it is more expensive, as 
a single engine of twice the force costs considerably less than 
the two. The engine, of the steam-boat North- America, 
is of this construction, and her speed is greater than that 
of any boat that has hitherto been constructed. Such also 
is the case in several of the best locomotive engines. 

A fly-wheel is not always an indispensable part of an 
engine, for there may be some of the machinery that is 
driven, that will act as a regulator in its stead. Thus, 
in steam-boats, where the wheels have a rapid motion, and 
in rail-way carriages, no fly wheel need be employed. 

70. The condensation of the steam is effected in the 
Condenser, both by keeping it constantly cool, and by ad- 
mitting a jet of cold water into that vessel. To accom- 
plish these objects, it is wholly immersed in a cistern sup- 
plied with cold water ; through an aperture in the side of 
the condenser, to which a stop-cock is adapted, a stream 
constantly spouts, the quantity of which is regulated, by the 
greater or less aperture, the stop-cock affords for the 
passage of the water. Steam at 212% is capable, as may 
be inferred from what has been stated on page 33, of 
heating six times its weight of water to the same tem- 
perature, and the united bulk is seven. The tempera- 
ture of condensation is usually 100% and to cool seven 



CONDENSING ENGINE. 133 

Pleasures of water of 212" to 100% will require about 
sixteen measures of water, which added to the six employ- 
ed in condensation is twenty-two. That is to say, twenty- 
two times the bulk of water evaporated by the boiler, is 
the least quantity that will suffice for the proper condensa- 
tion of steam, and cooling the condensed water. There 
must besides be a supply to prevent the water of the cistern 
from growing warm, and it has hence been usual to make 
the cold water pump supply a pint of water, for every cubic 
inch evaporated from the boiler. 

71. In order to save a part of the heat, the condensed 
Steam and water of condensation are delivered by the air 
pump into a vessel called the Hot Water Cistern, whence 
the water is raised, by the Hot Water Pump, to the feeding 
apparatus of the boiler. These two pumps are worked by 
rods, attached to the working beam, when the engine has 
one ; in other cases, these rods, with the rod of the air 
pump, are attached to a bar or beam, one end of which is 
adapted to the piston-rod, and rises and falls with it, the 
other is fastened to a fixed centre upon which it oscillates* 

72. The power of a condensing engine depends upon 
the state of the vacuum that is kept up in the condenser, 
as well as upon the pressure of the steam flowing from the 
boiler ; hence, it is important to be able to know, whether 
the rarefaction produced by the condensation of the steam, 
and the action of the air pump, be more or less perfect. 
This knowledge is attained by the Vacuum Guage. A 
glass tube open at both ends, has its lower extremity im- 
mersed in a basin of mercury, the other end communicates 
by a pipe, with the interior of the condenser. When the 
steam is condensed in that vessel, the pressure of the at- 
mosphere forces the mercury to rise in the tube, to a height 



134 DOUBLE-ACTING 

which is the measure of the exhaustion ; the difference be- 
tween the height of this column, and the height at which 
the mercury stands in a barometer, is the measure of the 
force, which acts in opposition to the pressure of the steam 
upon the piston of the engine. This must therefore be 
deducted, in estimating the actual performance of the 
engine, from the indications of the steam-guage, after an 
atmosphere has been added to the latter. An apparatus 
called the Indicator, in which a spiral spring is alternately 
opposed to the steam, and the vacuum has been proposed 
as a substitute for both the Steam and Vacuum Guages, 
but it has not yet come into general use. 

73, The action of the fly, in producing regularity of 
motion, reaches only to the inequalities that take place in 
the motion of the piston, during a single stroke. Should 
the flow of steam increase, the mean motion of the fly- 
wheel will be accelerated, and, should the flow be dimin- 
ished, the fly-wheel will uniformly be retarded. Neither does 
it control any change in the motion of the machinery, driven 
by the steam, unless that change be periodic. But it fre- 
quently happens that the quantity of steam, supplied by 
the boiler, fluctuates. Some regulator is, therefore, ne- 
cessary, which shall control the prime mover itself. For 
this purpose, a Governor is adapted to the steam engine. 
This is also required in cases where the quantity of work 
to be performed is fluctuating, as is the case in many 
branches of manufactures, where a part of the machinery 
may be suddenly stopped, or may be as suddenly connect- 
ed with the engine. The governor is an apparatus that is 
sometimes called a Conical Pendulum. Two heavy balls 
are suspended by bars to the opposite sides of a vertical 
axis. This axis is set in motion by the engine ; as it turns, 
the balls of the governor acquire a centrifugal force, which 



CONDENSING ENGINE. 135 

may be sufficient to overcome their weight, and cause them 
to diverge and fly off, performing hi their course a larger 
circle than before. As the balls fly off", they act, through 
the intervention of a system of levers, upon a valve that is 
situated in the steam pipe. This, vi^hich is called the 
Throttle-valve, has the form of a circular disk of metal, 
exactly filling up the pipe, when placed across it. It turns 
upon pivots placed at the opposite ends of one of its dia- 
meters, and may thus, either present its edge to the steam 
that passes along the pipe, in which case it hardly resists 
its course ; or may assume any intermediate position, until 
it close the pipe altogether. When the balls of the gover- 
nor revolve with so little velocity that the centrifugal force 
cannot overcome their weight, the levers place the throttle 
valve in the position that presents its edge to the steam ; 
when the velocity becomes great enough to throw out the 
balls to their utmost limit, this valve is thrown across the 
pipe, and shuts the passage completely ; with intermediate 
positions of the valves, the passage is more or less open, 
according to the rotary velocity of the governor. 

The governor is driven, by a strap that passes over a 
drum on the axis of the crank, or by wheels and pinions, 
deriving their motion from the same part of the engine. 

74. When the throttle valve acts to lessen the efflux of 
steam from the boiler, the elastic fluid will accumulate in 
that vessel, and its density and elasticity will increase 
along with its temperature. In this event it will act upon 
the float, counterpoising the self-regulating damper, which 
will descend and lessen the draught of the chimney. A 
diminution in the expenditure of steam thus acts to diminish 
the intensity of the fire by which it is generated, while, if 
it accumulate too suddenly, the safety valve afibrds it a 
vent. 



% 



136 DOUBLE-ACTING 

The valves, by which steam is admitted into the upper 
and lower parts of the cylinder alternately, and by which 
the communication with the boiler is opened and closed, 
are worked by machinery attached to the engine. Rack 
work upon the rod of the air-pump was originally used for 
this purpose, but it is now more usual to adapt an Eccen- 
tric to the axle of the crank. The eccentric is a circular 
plate of metal, that has an opening within it that just fits a 
part of the axle of the crank. This opening is placed in 
a position eccentric to the plate itself, and hence the appa- 
ratus derives its name. The eccentric plate is attached to 
the axle of the crank and revolves with it. A circular 
ring fits upon the eccentric, but leaves the latter a free 
motion within it ; any given point in this ring, will, there- 
fore, have its distance from the axis of the crank changed 
within certain limits ; this change is conveyed to a bent 
lever, that works the valves, through the intervention of an 
open frame work of the figure of an isosceles triangle^ 
whose two equal sides are tangents to the circular ring that 
encloses the eccentric plate. 

75. The Double-acting Condensing Steam Engine, then, 
is, in a great measure, self-acting. In truth, when applied 
to perform work with an uniform velocity, little is left to 
be done, except to supply the fire with fuel, and to observe 
the indications of the guages from time to time. Even the 
supply of fuel has been regulated by machinery driven by 
the engine, in such a way that it need not be fed for sever 
ral hours. 

76. The pistons of the Cylinder and air-pump, and the 
openings, in the covers of those parts of the engine, 
through which they move are rendered steam tight by 
packing. The substance employed for this purpose is 



CONDENSING ENGINE, 137 

hemp, in the form of plaited bands, and it is coated with 
grease. The joints of the several parts are closed by 
plaited hemp, or felt, coated with white lead ground in oil, 
or where one part is made to fit into another, by an iron 
cement, composed of iron filings, or gun borings, muriate of 
ammonia, and flour of sulphur ; the proportions are sixteen 
parts by weight of the first, two parts of the second, and 
one of the third substance. The joints are, generally 
speaking, formed by flaunches cast upon the pieces, 
in which holes are drilled ; through the latter, are passed 
screw bolts that are fastened by nuts. 

The power of machines is estimated in terms of some 
conventional force, taken as the unit. Steam engines 
having been originally introduced as a substitute for the 
action of horses, it became the practice to compare the 
force of an engine with the strength of a number of horses. 
The unit, which is employed in the estimate, is, therefore, 
a horse-power, and we speak of engines as being of the 
power of a certain number of horses. As the strength of 
horses is very various, this is still a vague method, and it 
becomes necessary that the estimate of the work, a horse is 
capable of performing, should also be agreed upon. Differ- 
ent engineers have at different times made use of different 
valves, but the modes of estimating the horse-power, re- 
solve themselves, into the expression of the number of 
avoirdupois pounds, raised one foot high in a minute. 

Desagnliers estimates this number at 27,5001bs., and 
Smeaton 22,9161bs. Watt supposes that a horse is able 
to raise 32,0001bs. ; but in calculating the power of the 
engines of Watt and Bolton, the estimate is taken as high 
as 44,0001bs. 

The force which acts is the pressure of the steam upon 
the piston ; this, multiplied by the velocity of the piston, 
gives the whole power of the steam ; but before the steam 

18 



138 DOUBLE-ACTING 

that issues from the boiler can reach the piston, it is re- 
tarded by the friction of the pipes, and loses by cooling a 
part of the expansive force indicated by the steam-guage ; 
its action is next diminished by the cooling it undergoes in 
the Cylinder itself, and before the power is transmitted to the 
working point of the engine, it must overcome the friction 
of the piston, open and shut the valves, force the steam into 
the condenser, and work the air-pump, and the hot and 
cold water pumps. It has next to overcome the friction 
of the axles of the lever-beam, parallel motion, and crank ; 
and the piston is besides resisted by the uncondensed steam 
remaining in the condenser. Of the last, the vacuum 
guage furnishes a measure, but of all the rest nothing is 
known perfectly, except by comparing the work actually 
performed, with the original force of the steam. It has been 
deduced from observation upon the working of engines, that 
more than 40 per cent, of the original power of the steam 
is expended upon these several resistances, hence the indi- 
cation of the steam-guage must be diminished in that ratio 
at least, before it is employed in the calculation of the force 
of the engine. 

In this country, it is usual to estimate the horse power 
at 33,0001bs., raised one foot per minute, and the mean 
pressure of the steam, in a condensing engine, at lOlbs. per 
square inch. We hence have the following rule : 

JMultiply the area of the piston in square inches by 10, and 
by the velocity of the piston in feet per minute ; divide the con- 
tinued product of these three quantities by 33,000, the quo- 
tient is the estimated force of the engine in horse power. 

The rule of Brunton gives 44,0001bs. for the divisor, and 
that of Tredgold reduces the mean pressure to 9,10 pounds 
per square inch, which would correspond to a divisor of 
nearly 36,000, when the pressure is assumed at lOlbs. 
The indication of the steam-guage is supposed to be five 



CONDENSING ENGINE. 139 

inches of mercury, equivalent to a pressure of 2ilbs. more 
than an atmosphere, or 17ilbs. per square inch. The 
safety valve is loaded with a weight of three pounds per 
square inch, which, with the aid of the atmosphere, will re- 
tain steam whose expansive force is not greater than 181bs. 
per inch. 

77. The quantity of water to be evaporated in order to 
do the work of a horse in a double-acting condensing en- 
gine, regulated as we have just stated, may be estimated as 
follows, viz. 

A cubic foot of water, evaporated under the ordinary 
pressure of the atmosphere, occupies a space 1696 times 
as great as it did before ; but the space it occupies under a 
pressure of 17| pounds is, if we abstract from the expan- 
sion by temperature, less in the ratio of 15 to 17i, for 
elastic fluids occupy spaces inversely proportioned to the 
pressures by which they are confined, (see p. 24) ; hence 
the space occupied by steam having an expansive force of 
17^1bs. is 1454 times the original bulk of the steam. 

A cubic foot of water, therefore, occupies a space, in the 
form of such steam, of 1454 cubic feet; and the effective 
pressure, as we have before stated, is lOlbs. per square inch 
or 1440lbs. per square foot ; the power of a cubic foot of 
water is therefore, to lift 1440x1454 or 2,0937601bs. 
through the space of a foot. If this be divided by 33,000, 
which is the conventional weight to be lifted by a horse 
power per minute, it will give the number of minutes in 
which,' if a cubic foot of water be evaporated, it will 
keep up this conventional unit of force. The quotient is 
63, or three minutes more than an hour. It is therefore 
usual to allow the evaporation of a cubic foot of water per 
hour to be equal, in the engine under consideration, 
to a horse power : and as it is well to be always certain of 
a supply of steam, boilers are made to furnish more units 



140 DOUBLE-ACTING, &C. 

of steam than the engine is estimated at ; the waste of 
heat in small boilers being greater in proportion than in 
large ones, this excess is a constant quantity, the boiler 
being calculated to produce steam equivalent to two horse 
power, more than the estimated force of the engine. We 
have seen that a surface of boiler in contact with flame 
and hot air of 8 square feet (see p. 72) is equal to the 
conversion of this quantity of water into steam. 

78. The feeding apparatus of the boiler which is as we 
have seen, composed of a pump that raises the water of 
condensation, from the hot water cistern to a cistern at 
the top of the feed pipe, must therefore supply, at least 
one cubic foot per hour, for each horse power at which the 
force of the engine is estimated ; or y^V^ part by bulk of 
the capacity of the cylinder, at each stroke of its piston. 
As, however, it is better to have an excess than a defect of 
water, the hot water pump usually raises, at each stroke 
^i^th part of capacity of the cylinder. 

Such are the general principles of action of one form 
the condensing engine, which, to distinguish it from others 
in which the same operation is employed to form a vacu- 
um, is called the Double-Acting Engine, to which epithet is 
also added the name of the inventor. Watt. We are now 
prepared to enter into a more particular view of its several 
parts, the use and operation of which would have been unin- 
telligible, had we not previously investigated their uses, 
and the relation in which they stand to each other. 



CHAPTER V. 

DESCRIPTION OP THE DOUBLE-ACTING CONDENSING 

ENGINE. 

Usual form of Double-Acting Condensing Engine. — Steam,' 

pipe, Jacket. Side Pipes. Slide Valve. Puppet 

Valve. — Cylinder. — Cylinder Lid. — Cylinder Bottom. — 
Piston. — Woolps Piston.— Car twrighVs Metallic Packing. — 
Condenser. — ^ir Pump. — Delivering Door. — Air Pump 
Bucket. — Hot Water Cistern and Pump. — Cold Water 
Cistern. — Injection Cock. — Water of Condensation. — 
Cold Water Pump. — Parallel Motion. — Lever Beam. — 
Pump Rods. — Connecting Rod. — Crank. — Fly Wheel. — 
Tumbling Shaft. — Eccentric. — Double Eccentric. — Adjust- 
ment of Eccentric. — Governor. — Throttle Valve. — Other 
forms of Double-Acting Condensing Engine, — Mode of 
setting these Engines in motion, 

79. Having in the last chapter explained the general 
principles of action of the Double Condensing Engine, 
we shall now proceed to describe the several parts more 
particularly, and in reference to a plate, on which they are 
figured in connexion with each other. See PI. IIL As 
the condensing engine, in its most complete and perfect 
form, is in more general and frequent use in Great Britain 
than in this country, an engine constructed by Messrs. 
Murray, Fenton & Wood, of Leeds, has been chosen for 
the illustration of this part of our subject. 



142 DOUBLE-ACTING 

Fig. I. is an external elevation of this engine. Fig. II. 
a section. Fig. III. a horizontal plan. Fig. IV. a view of 
the lower part of the apparatus from the opposite side. 
The same letters apply to the same parts in these four 
several figures. 

In the engine before us, the steam reaches a part of the 
steam pipe marked s whence it flows into a space formed 
around the Cylinder by a cylindrical case called the Jacket. 
The use of this is to keep the Cylinder itself at an uniform 
temperature. All engines have not this additional part, 
and in this country in particular we never recollect to have 
seen it used. For it, is frequently substituted a simple 
casing of wood, which, being a bad conductor, has been 
supposed, well adapted to preserve the heat of the 
cylinder. 

From what has been said, in respect to the mode in 
which heat is carried off, under certain circumstances, it 
will appear that both the Jacket and wooden casing are 
liable to objections. In the air, but little heat is carried 
off in consequence of the conducting power of the surface, 
and by far the greatest part of the loss is due to radiation. 
Now of the metals, the rough blackened surface of cast 
iron is among the best radiators, and wood stands high in 
the general order of radiating power, and hence, in the 
first case, the steam will be cooled before it reaches its 
place of action ; and in the second, the temperature of the 
Cylinder will be more affected than if it had not been 
cased. The principles we have discussed would point out 
as a sure method of retaining the heat, to enclose the 
cylinder in an air-tight cylindrical case of some bright 
metal, with a thin body of air between them. The confined 
air will convey but little heat to the casing, and that which 
is conveyed will radiate very slowly. 



CONDENSING ENGINE. 143 

80. In the engine before us, the steam passes from the 
jacket to the side pipes, marked a a, through the opening 
marked h. The form and arrangement of these pipes 
depends upon the structure of the valves ; in this engine 
the valves are of that description called the Slide Valve. 
This was originally invented by Murray, of Leeds, but was 
comprised by him within a shorter space, the valve before 
us which occupies the whole side pipe is an improvement 
of Watt's. 

81. The side pipe has the general figure of a half cylin- 
der, the plane face of which is turned towards the Cylinder 
of the engine, and is terminated at top by a square box. 
The steam enters this pipe by a channel 6, that communi- 
cates with the jacket. In engines that have no jacket, the 
steam-pipe usually enters the side-pipe from behind it, about 
the middle of its height. 

Within this pipe is placed another, which exactly fills it 
at the upper and lower extremity, but which is made less, 
in the middle, so that the steam on entering the side-pipe 
fills up the space between the two pipes. The inner pipe 
is moveable, and attached to a rod that passes through an 
air-tight collar, in the square box, of which we have spoken, 
and by which it is drawn up and pushed down alternately, 
by a mechanism that will be hereafter described. 

Between the Cylinder and the outer pipe are two chan- 
nels whose section is rectangular. One of these forms a 
communication with the upper, the other with the lower 
part of the Cylinder. 

The length of the inner pipe is so adjusted that when 
that part, at one of its extremities, which just fills up the 
outer pipe, is opposite to the corresponding rectangular 
passage, the other rectangular passage shall be opposite to 
the space that we have described as left between the mid- 



144 DOUBLE-ACTING 

die part of the inner, and the outer pipe. Hence, steam 
will flow into the Cylinder from this space. In the plane 
surface of the part of the inner pipe that is applied to the 
first named rectangular passage, there is a corresponding 
rectangular opening, by which the steam, from the adjacent 
side of the piston, will pass into the inner pipe, and thence 
by a passage marked o into the condenser n. In the posi- 
tion in which the engine is represented in the figure, the 
steam is flowing into the lower part of the Cylinder, and 
beneath the piston, while it is passing out at the opposite 
end, and through the inner pipe to the condenser. 

The inner pipe has a similar rectangular opening at its 
opposite extremity ; when, by the action of the engine, the 
inner pipe changes its position, this opening adapts itself 
to the adjacent rectangular passage, while the other com- 
municates with the space between the two pipes, and thus 
the direction of the steam and the motion of the piston 
are reversed. 

It will therefore be seen, that there is a constant com- 
munication, between the space contained between the two 
pipes, and the boiler, while the inner pipe has a constant 
communication with the condenser. A change in the 
position of the inner pipe brings the openings of the Cylin- 
der alternately into communication with the boiler, and 
condenser. 

It is obvious that this species of valve requires very per- 
fect workmanship ; the plane surfaces of the outer and 
inner pipe must be ground in the most careful and exact 
manner, and the circular surfaces, where they come in con- 
tact, at the upper and lower extremities must also be accu- 
rately fitted. 

The structure and use of this species of valve will be 
better understood by reference to the following figures, in 
which it is represented in two different positions. In order 






DOUBLE-ACTING 



145 



to give more variety, v^e have taken a form, different from 
that of the engine, in PL III. in which the spindle enters 
the side pipe from above, w^hile in the figure, the spindle is 
applied beneath. 



-H! CD 

tliiiiiuiliuniiiiiii 



Bjliii f 



19 



146 DOUBLE-ACTING 

This valve has the advantage, which is in most cases 
important, of opening gradually, and thus causing no sud- 
den shock when the motion of the engine is changed, 
and by a proper adjustment of the distances between the 
openings of the inner pipe, and of the apparatus by which 
it is driven, it may be made to cut off the steam, before the 
motion of the piston is completed, and thus again render 
the change less sudden. On the other hand, the accuracy 
of workmanship it requires may not be always attainable, 
and its repair cannot be effected, in situations remote from 
well-organized workshops. It is also to be stated, that 
when impure water is used, it has been found to wear 
rapidly and unequally, and thus, after having been intro- 
duced in many of our steam-boats, it has been laid aside, 
and another, and more ancient species of valve restored 
in its place. Of this we shall proceed to give a description. 

82. This species of valve, usually called the puppet valve, 
is represented on Plate II, Fig. 3. 

The side pipes are two in number, of which that marked 
A, is continually receiving steam from the boiler, through 
the steam pipe e, while that marked B is constantly con- 
veying it to the condenser. These pipes are united by be- 
ing both inserted at each end into the same cylindrical case, 
or box, at which there are consequently two, at C and D. 
Each of these boxes is divided into three spaces, by two 
diaphragms, having each an opening of the form of a trun- 
cated cone, whose least base is lowermost. These apper- 
tures are called nozzles, and are the seats of the valves ; 
to fhese nozzles, four solid frusta of cones, a, b, c, d, are 
accurately ground, and form the valves ; from the space 
between the two diaphrams in each box, is an opening that 
allows the steam to pass to and from the cylinder. 

It will be obvious, that when the two upper valves, a and 



CONDENSING ENGINE. 147 

€, in each box, are raised, steam must flow from the boiler 
into the Cylinder, and when the two lower of each set, b and 
cZ, are raised, it must flow from the cylinder to the conden- 
ser. Hence, it is necessary that they should reciprocate, 
the valves a and d opening when the valves b and c close, 
and vice versa. Hence, the two valves, a and d, are united, 
and made to open and shut at the same time ; as are the 
two valves b and c. It will be perceived by the drawing-, 
that each valve has a cylindrical spindle attached to it, and 
the four nozzles are in the same vertical line. The spin- 
dles of the two steam valves, a and c, are hollow, and ad- 
mit the spindles of the two condensing valves, b and d, to 
pass through them. The purpose of this will be explained 
hereafter. In more ancient forms of the engine, the spin- 
dles were replaced by a short rack, into the teeth of which 
the teeth of a circular segment caught. The use of this 
form will also be stated hereafter. 

These side pipes sometimes have, for the sake of orna- 
ment, the form of pillars, the entablature being extended 
above to cover the space left vacant by the side pipes. 

The rule for the size of these nozzles is, to make their 
least diameter one-fifth, at least, of the diameter of the Cy- 
linder. The passages into the boiler must have an equal 
area, as must the passages of the slide valve that has just 
been described. There are also cases, where the size of the 
nozzle may be advantageously increased beyond this mini- 
mum. 

83. The Cylinder of a steam engine has the figure which is 
denoted by its name, and in order to avoid ambiguity, it has 
been and will always be distinguished by beginning it with 
a capital, in order to prevent its being confounded with 
such other parts as have also a cylindrical form. It is 
represented in the figures on Plate III, by the letter b. 



148 DOUBLE-ACTING 

This vessel is in all large engines, made of cast iron, cast 
with a core, and reamed out to the proper size. This 
operation requires great care, and should be done in a mill 
liable to no agitation, for much of the value of the engine 
will depend upon the interior being as truly a mathematical 
cylinder, as the nature of materials will admit. Near the 
upper end of the Cylinder is cast a rectangular piece, in 
which is the passage /i, and at both ends are cast flaunches 
to admit the fastening of its lid and bottom, by means of 
screw-bolts and nuts. In the engine on the plate, the lid 
is screwed to a flaunch on the jacket, and the flaunch of 
the Cylinder secured to the jacket by packing. 

84. The lid of the Cylinder is a circular plate, whose dia- 
meter is equal to that of the flaunch to which it is adapted. 
On its lower side, it is turned, so that a circular projection 
fits the inside of the Cylinder, leaving barely room for the 
packing. In the middle is an opening to admit the passage 
of the piston-rod, and around this opening is cast a cylin- 
drical box, on the upper side of the lid, to receive the pack- 
ing, by which the rod is made to work steam tight. The 
upper part of this box is cut into the form of a female 
screw, to receive the screw that compresses the packing, 
and the head of the former is turned into the form of a 
cup, to contain oil. 

85. The bottom plate of the Cylinder is of the same dia- 
meter with the top, and has a similar projection turned 
upon it, to fit the Cylinder. The lower steam passage 
passes through it, and is cast in one piece with it. In the 
engine before us, the flaunches of the Cylinder and the 
jacket are united to the bottom, by the same set of screw- 
bolts and nuts. 

The length of the Cylinder must be as much more than 



CONDENSIING ENGINE. 149 

the length of the stroke of the piston, as is equal to the 
thickness of the latter, and, in addition, a small space to 
prevent the piston from striking. In the engine on Plate 
IIIj the diameter of the Cylinder is equal to half the length 
of the piston's stroke. This proportion is not a constant 
one, but is that sanctioned by the general practice of Watt. 
In the English steam-boats, where the engine is placed be- 
neath the deck, the stroke is necessarily short, and power 
is gained by increasing the diameter of the Cylinder. 

We shall have occasion, in speaking of steam-boats, to 
treat of the proper length of stroke, for engines intended to 
propel them. In those which are applied to manufac- 
tures, the proportion stated above, is perhaps the best. 

86. The piston is composed of two pieces of circular 
section, that are just so much smaller than the internal 
section of the Cylinder, as to move in it freely without 
touching. The lower piece is firmly attached to the piston- 
rod, by making the lower end of this rod of the shape of a 
truncated cone, of which the lesser base is uppermost, and 
of the same size with the rod. A key is passed through 
the rod, just above the piston and unites them firmly. 

The two pieces of which the piston is composed are 
connected by screws, and have a semicircular groove cut out 
of their united mass, forming a ring completely around them. 
This open ring is occupied by the packing. The packing 
is usually formed of hemp, moistened by an oleaginous 
substance. This packing is compressed and made to apply 
itself closely to the sides to the Cylinder, by the screws 
which unite the two pieces of which the piston is com- 
posed. As the packing wears, the screws are turned, and 
thus the packing, being again compressed, is forced out 
and again applies itself to the cylinder. This arrangement 



150 



DOUBLE-ACTING 



may be better understood by the following figure, which 
represents a section of the Piston, a is the Piston-rod 
terminating in the tfuncated cone b ; c c screws to unite 
the two parts of the piston, d d and e e ; //section of the 
packing. 




87. An ingenious mode of tightening the packing without 
taking off the lid of the cylinder was invented by Woolf. 
The head of each of the screws, is cut into the form of a 
toothed pinion, and the teeth of all these work in a wheel, 
having a free motion around the piston-rod. It is there- 
fore evident that if one of the pinions be turned, not only 
will the screws attached to i1, be made to act, but all the 
others will be equally driven forward. One of the screws 
has a square head, which can be reached by a key passed 
through an opening in the lid of the Cylinder, and which 
is usually closed by an air-tight cap; thus it may be turned, 
by removing the cap, and all the others will be turned 
equally by the wheel and pinions. 



CONDENSING ENGINE 



151 



In the figure annexed a is the piston rod, h h the wheel 
fitted loose upon it, c, c, c, c, c pinions forming the heads of 
the screws tliat compress the packing, d square head formed 
upon one of the screws, by adapting a key to which, the 
wheel 6 6 is tuined, through the intervention of the pinion 
to whose screw the key is applied, and turns the remaining 
pinions, and with them the compressing screws. 




88. A metallic packing invented by Cartwright appears, 
in the opinion of a very intelligent artist, Hkely to super- 
sede all others. Two rings of metal, accurately ground to 
fit the cylinder, are interposed between the upper and 
lower parts of the piston. Each of these rings is cut inta 
three parts, and they are placed upon each other, in such a 
manner, that the joints of the one ring fall half way between 
the joints of the other, in the same manner as the break- 
joint of masonry. Three springs are made to act upon 
each of these rings, one at each joint, and thus to press the 
two adjacent pieces outwards. In this manner the springs 
carry the rings outwards, to replace any diminution by wear, 
and the breaking of the joints prevents any escape of steam 



152 



DOUBLE-ACTING 



through the apertures, that are thus made in either of the 



rings. 



The figure helow shows this arrangement, where a is the 
piston-rod, 6, 6, h springs that press against the joints c, c, c 
of one of the rings, which is here represented as formed 
by inscribing an equilateral triangle in a circle, cZ, c?, d are 
parts of the three pieces that form the second ring, whose 
joints fall at the points e, c, c, against which springs similar 
to 6, 6, h press. 




In applying a metallic piston, accuracy in the boring iis 
absolutely essential, nor can they be introduced except 
when this part of the workmanship is of the best descrip- 
tion. 



89. The Condenser is a vessel of a cylindric form. It 
is represented in Fig. 2, PI. III. by n. Through the top 
passes the pipe o, that conveys the steam from the valves 
of the engine. On the side is an aperture, to which is 
adapted the valve r, called the Injection-cock, the use of 



CONDENSING ENGINE. 153 

which is to admit a constant jet of cold water to condense 

the steam. The capacity of the condenser, when the engine 

works with steam of the pressure of 17|lbs. per inch, is i 

usually one-eighth part of the capacity of th*e Cylinder. ^\ 

The state of the vacuum in the condenser is ascer- 
tained by means of a vacuum guage. This is represented 
PI. I. Fig. 14. a a is an open vessel of mercury, b ba glass 
tube immersed at one end in the mercury, and communicat- 
ing at the other with the condenser through the tube e. 
As the vacuum is formed in the condenser, the pressure of 
the external air will force the mercury up the tube b 6, 
and the difference between the height to which it rises, and 
that at which the mercury of the barometer stands at the 
time, marks the resistance the gaseous matter, that cannot 
be withdrawn from the condenser, offers to the descent of 
the piston. 

The Condenser communicates with the Air-Pump by a 
horizontal passage of a rectangular shape. In this passage 
is situated the Foot-valve t. This has usually the form of 
a shutter hanging by a hinge on its upper side, in a posi- 
tion slightly inclined from the vertical, and closing by its 
own weight. The valve is fitted to its seat by grinding. 
The condenser and air-pump are screwed down to a com- 
mon base called the bed-plate. 

90. The Air-pump q is also a cylindrical vessel, almost 
identical in figure with the Cylinder, but having but half 
the lineal dimensions, and consequently one-eighth of the 
capacity, or one just equal to that of the condenser. The 
lid of the air-pump is similar to that of the Cylinder, per- 
mitting the passage of the rod through a stuffing-box. 

91. The piston of the air-pump is packed in the same 
manner as that of the Cylinder, but unlike it, is not solid. 

20 



154 



DOUBLE-ACTING 



It contains a valve, which is usually of that form called the 
butterfly valve. In this shape, the Piston-Rod is attached 
to a bar extending across the piston, in the direction of one 
of its diameters ; to this are adapted by hinges, in such a 
manner as to open upwards, two shutters that fill up the 
rest of the circular opening of the piston. These shutters 
therefore rise and fall together like wings, whence their 
name. The piston and its valves are usually called the 
Bucket of the Air-pump. From the dimensions we have 
stated above, it will be obvious that the stroke of the 
Bucket is just half that of the Piston of the Cylinder. A 
plan and section of an air-pump bucket are represented be- 
neath. 




CONDENSING ENGINE. 155 

92. On the side of the Air-Pump, and near its top, is 
cast a rectangular passage, which is closed by a valve v, 
similar in form and structure to the foot-valve, and which 
is called the Delivering-door. 

93. Upon the rise of the bucket of the Air-pump, the 
water of condensation is discharged by the delivering-door 
into a rectangular vessel of iron w, called the Hot-water 
Cistern. The Hot-water Pump, by which the water of 
condensation, or at least as much of it as is necessary for 
the supply is carried to the boiler, is represented at x. It 
is a common pump, composed of a barrel and two valves. 
The water converted into steam is as we have seen on page 
133, --i--th part of the capacity of the Cylinder, for each 
stroke of the piston ; the pump is made to furnish a greater 
quantity, or ^ |o^^ part, in order that there may be no risk 
of a defect in the supply. 

As the water of condensation is much greater in quanti- 
ty than this, being twenty-two times as much in weight as 
the steam that is employed, a large portion of the water 
must run to waste, which it does by a waste-pipe. 

The calculation of the size of the hot-water pump, may 
be made as follows, viz. 

Divide the cvMc contents of the cylinder in inches by 900, 
and this quotient by the length of the stroke of the pump, the 
quotient will be the area in square inches, ichence by the usual 
geometric rule the area of the valves may be calculated. 

The stroke of the hot-water pump in the engine on PI. 
HI., is one-third of that of the cylinder. 

94. The condenser and air-pump are immersed in a cis- 
tern of water, called the cold-water cistern. In some 
engines this is a basin in the ground, lined with masonry, 
laid in cement. In steam-boats it is sometimes of wood, at 



156 DOUBLE-ACTING 

other times is omitted altogether. In other engines again, 
it forms a cast-iron trough or basin, on the sides of which 
the whole of the apparatus is supported. In the engine 
represented on PL III , this is the case, as will be obvious 
from the several views in which it is represented, a a being 
this trough. An engine thus supported, and which may 
therefore be placed upon any sohd basis, entirely independ- 
ent of walls or buildings, is called a portable engine, even 
when of the largest dimensions. 

95. From the cold-water cistern, a pipe passes into the 
condenser. The use of this is to admit a jet of water, to 
condense the steam with greater rapidity, by bringing it in 
contact with a greater surface. The extremity of this 
pipe is sometimes covered by a nozzle, pierced with holes 
like that of a watering pot. The quantity of injection 
water is regulated, by a valve called the Injection-cock, 
which is to be seen in Fig. 2. 

96. As the injection-cock is constantly drawing water 
from this cistern, and as the water it contains is constantly 
abstracting heat from the condenser and air-pump, it re- 
quires a constant and regular supply, as well to keep it at a 
proper temperature, as to renew what is actually expended. 
For this purpose the cold-water pump y is provided. It, like 
the hot-water pump, is a common pump, communicating 
with a reservoir of fresh water. We have upon page 133, 
stated the quantity of water that is needed, to keep the 
water in this cistern at the proper temperature, whence the 
area may readily be calculated when the length of the 
stroke is known. The length of the stroke of the cold- 
water pump, in the engine before us, is the same as that of 
the air-pump, or half that of the Cylinder. 



CONDENSING ENGINE. 157 

97. The theory and use of the Parallel Motion, 1, 2, 3, 4, 
has already been explained— see pages 121, 122, 123. The 
rule for one of its most usual forms is as follows, viz. The 
parallel bar is half the length of one arm of the working 
beam, or one-fourth of the distance between the two glands. 
The radius-bar is of the same length with the parallel-bar. 
The two pairs of straps are, of course, of equal length, 
and are usually three inches less, between their centres, 
than the length of the half stroke of the piston-rod. 

The centre, to which the air-pump rod is attached, is in 
the inner pair of straps at the point where a line drawn 
from the fulcrum of the lever-beam, to the upper end of 
the piston-rod, cuts the inner strap. Seepage 122. 

98. The length of the lever-beam, in Watt's engines, is 
usually one and a half times the length of stroke of the 
piston-rod. The beam is usually cast in one piece. The 
pivots of the parallel motion, pump rods, and connecting 
rod being turned upon projecting pieces cast upon it. 

99. The air-pump rod u being attached to the inner pair 
of straps, is at a distance, from the centre of motion of the 
lever-beam, of one-fourth of the length of the latter. 

The rod of the cold-water pump is attached to the lever- 
beam, at an equal distance from the fulcrum on the oppo- 
site side. 

The rod of the hot-water pump is at a distance, from the 
fulcrum, of one-sixth of the length of the working beam. 

The length of the connecting rod between the centres, in 
Watt's engines, is twice the length of the stroke of the 
piston. 



158 DOUBLE-ACTING 

100. The arm of the crank r, is half the length of the 
stroke of the piston, in all cases where the arms of the 
lever-beam are of equal length. 

101. The radius of the Fly- Wheel may be various, accord- 
ing to the uses to vs^hich it is applied ; the motion for driv- 
ing machinery ought to be taken off at a distance from its 
centre, equal to that of its centre of gyration. See page 
16. In the engine on PI. III., the fly-wheel has a radius 
equal to twice the whole length of the cylinder. The 
weight is calculated by the following rule : 

•Multiply the number of horse's powers of the engine hy 2000, 
and divide hy the square of the velocity of the circumference 
of the wheel per second, the quotient is the iveight in cwts. 

The velocity of the circumference is readily found, when 
the radius is given, for the crank has a velocity as much 
greater than that of the piston-rod, as the circumference 
of a circle is greater than its diameter, and the circumfe- 
rence of the fly-wheel has a velocity as much greater than 
the crank, as the radius of the former is greater than that 
of the latter. 

In the first form of Watts' engines, the valves were open- 
ed and shut b)^ apparatus of the same description with that 
which had been used in the more ancient forms. Tappets 
were attached to the rod of the air-pump, which, during 
the ascent and descent of the rod, acted upon levers 
with counterpoising weights. These levers were thus 
made to give a reciprocating motion to toothed segments, 
that acted upon racks attached to the valves, and thus 
opened and shut them. We shall return to this manner of 
working valves in the history of the engine. 

When conical valves are used, at the present time, a 
spindle is attached to each, and the nozzles are immediate- 
ly beneath each other. Thus the two spindles of each 



k 



CONDENSING ENGINE. 159 

pair of valves are in the same vertical line ; the upper 
spindle in each pair is hollow, and the spindle of the lower 
valve passes through it. The weight of the valves is usual- 
ly sufficient to close them, and keep them shut, if not, they, 
are loaded until they shut themselves. In order to open 
them, the following arrangement is employed. The spin- 
dles of the two valves, that are to act simultaneously, as for 
instance, the steam valve of the upper pair, and the con- 
densing valve of the lower, are united hy rods, which have 
consequently the form of three sides of a rectangle. These 
rods are pressed upwards at a particular part of the motion 
of the engine, by pieces projecting from a horizontal shaft 
that has an oscillating motion. These projecting pieces or 
arms lie in the same plane, and on opposite sides of the 
shaft, so that when one of them acts upon the rod that 
moves one pair of valves, and presses them upwards, the 
other ceases to act, and permits the other two to fall into 
their seats, by their own weight. The return of this oscil- 
lating shaft permits the first pair of valves to shut, and 
causes the other piece, or arm, to act upon the two that 
were before shut. 

102. This oscillating shaft is called the Tumbling Shaft. 
It receives its motion by means of a small crank that is 
attached to it, and moves upon it as an axis. This crank 
is connected with the axle of the fly-wheel, by an ap- 
paratus called the Eccentric. This is represented in 
Figs. 1 and 2, on PI. III., and is shown separately in 
Fig. 4. 

A circular plate b has' an opening of a circular shape 
cast in it, but having an eccentric position in respect to it. 
This last circle just fits the shaft of the fly-wheel, and is 
wedged firmly to it, so that the latter carries the circular 
plate 6, around with it in its revolutions. 



160 DOUBLE-ACTING 

To the circular plate is fitted a circular ring c, within 
which it can turn, and which therefore need not receive 
any motion from it, but what arises from the eccentricity of 
the revolution of the plate. To this ring are attached two 
bars df e, forming the sides of an isosceles triangle. These 
are united by frame work. These bars terminate in a 
single piece, in the direction of a perpendicular to the base 
of a triangle, and which has a handle / turned upon its 
extremity. The use of this handle is to lift the eccentric 
from its place, when it is wished to stop the engine, and 
return it again, when the engine is to be set in motion. A 
notch of a semicircular figure is cut in the eccentric, which 
drops upon a pivot, turned upon the crank of the tumbling 
shaft g. 

It will be obvious, that while the axis of the fly-wheel is 
carried around, and with it, the circular plate, the end of the 
triangular frame will have an oscillating motion communi- 
cated to it, which the free motion of the ring c, will allow 
to be converted into a reciprocating circular motion, in the 
crank of the tumbling shaft ; it will thus give the latter, a 
motion suited to the opening of the valves, by means of the 
two arms that have been described. 

The engine upon the plate (PI. III.) has, as has been 
described, a slide valve. This is set in motion in a manner 
different from the puppet valves. 

An arm, h, projects from each end of the tumbling shaft, 
and both are in one plane at right angles to its crank, g, f. 
To these arms are attached two light connecting rods, 
that rise above the side-pipe, where they are united by a 
cross-head. To the middle of this is attached the rod that 
moves the slide, and thus the latter is both raised and de- 
pressed by the action of the eccentric, while, as we have 
seen, the puppet valves are raised only, and retiim to tbeif 
seats by their own weight. 



CONDENSING ENGINES. 161 

103. When an engine is used for purposes that occasion- 
ally require its motion to be reversed, two eccentrics may 
be employed, that adapt themselves to cranks situated at 
the opposite ends of the tumbling-shaft, in planes at right 
angles to each other. Only one of these eccentrics is used 
at a time ; when it is necessary to reverse the motion of 
the engine, the piston is stopped at half-stroke, or in the 
position represented in Figs. 1 and 2, on PL III. The ec- 
centrics are then exchanged; that before in use being raised, 
and the notch of the other dropped upon its crank. When 
the steam again flows, the piston will return in a direction 
opposite to that in which it was proceeding when stopped. 
Another method that has been used in some English steam- 
boats, consists in cutting two notches opposite to each 
other in the rod of the eccentric, the rectangular cranks of 
the tumbling-shaft are at the same end of the shaft ; the 
eccentric lies between them, and may be made to apply 
itself to either at pleasure. 

104. It will be obvious, that the time at which the valves 
open and shut, may be determined by the position of the 
eccentric upon the shaft of the fly-wheel. This may be 
done, by this apparatus, far better than it can be by tappets 
upon the rod of the air pump, or as they are usually call- 
ed, a plug-frame. This determination is of no small impor- 
tance to the working of an engine. Should the piston be 
impelled by the steam to the very end of its stroke, a vio- 
lent blow will take place between it and the head or bottom 
of the Cylinder, while on the other hand, if the steam- 
valves be opened too soon, a part of it will be expended 
in diminishing the action of the steam on the opposite side 
of the piston. In both cases, power will be wasted, and 
in that form it will be exerted to injure the apparatus. In 
putting up an engine, the position of the eccentric is deter- 

21 



162 DOUBLE-ACTING 

mined by actual trial, and the eccentric is left in the posi- 
tion where it is found to tend most to the equable and regu- 
lar working of the engine. 

105. A band passing over a drum on the axis of the fly- 
wheel turns a second drum which is upon the axis of a bevel 
wheel. This bevel wheel gives a motion to another, that car- 
ries upon its axis the Grovernor. This arrangement is^epre- 
sented upon the plate, but could not be distinguished by let- 
ters. This governor, as has been stated, is a conical 
pendulum. The weights revolve in the same plane, which 
is raised by their centrifugal force, when the velocity in- 
creases, and falls as the velocity of rotation diminishes. 
The theory of this instrument shows, that its revolutions 
are half the number, that would be performed by a pendu- 
lum, the length of which is equal to the distance of the 
plane, in which the centres of the balls revolve, from the 
point where the bars, by which they are suspended, cross 
each other. Thus, then, if the least and greatest number 
of the revolutions that it is intended that the fly-wheel shall 
perform, in a given time, be known, it will be easy to cal- 
culate the length of the conical pendulum. 

106. The rods that bear the balls of the governor are 
united by pivots to two others, also connected by pivots, 
andsliding at their point of union, upon the axis of the gov- 
ernor. The parallelogram that it thus formed, is some- 
times above the joint whence the balls hang, as in the hori- 
zontal engine on Plate VI, and sometimes below it, as in 
the high pressure engine on Plate F, or the separate fig- 
ure of the governor on Plate /F", Fig. 2. In either case 
it gives motion to a lever, which acts at its opposite end 
upon a rod, that moves the handle or lever of the throttle 
valve. This system of levers is so arranged that the 



CONDENSING ENGINE. 163 

throttle valve is opened to its utmost limit, when the balls 
of the governor are in their lowest position, and is wholly 
closed, when they have been thrown out to their greatest 
extent, by the centrifugal force. In the first case, therefore, 
all the steam that is generated, flows to the engine, in the 
last, it is wholly cut off. 

107. The form of double-acting condensing engine which 
we have thus described, is that which is most commonly 
used in manufactures, particularly in Europe. It cannot, 
however, fail to have been remarked that it contains, at 
least, one part by no means necessary to its action : This is 
the lever beam. The engine, as we shall see hereafter, 
was originally applied to the single action of pumping wa- 
ter, and in this, the pump-rod, or brake was conceived to 
be essential ; this, when made with equal arms became the 
lever beam. Successive advances towards perfection in the 
structures were made, as improvements on the original 
plan, and not as original inventions. It has thus happened, 
that an unnecessary and cumbrous part of the apparatus 
has been perpetuated. A far more simple form of the en- 
gine, and which is in many cases preferable, is that which 
was used by Fulton in his steam-boats, and of which one 
is represented upon Plate VII. It will be at once seen by 
inspection, that in this engine, the beam is suppressed, to- 
gether with the parallel motion. As a substitute for these 
parts, a cross-head a is adapted to the upper extremity of 
the piston-rod, b ; this works between vertical guides, a a ; 
it is connected to the two cranks, c c, by the two connect- 
ing rods, b b b b, and to these is joined, in the case before 
us, the axis of the water-wheels, d d ; the axis of the fly- 
wheel might in like manner be turned by these cranks, 
were it intended to apply the engine to general purposes. 



164 DOUBLE-ACTING 

The pumps are worked by a beam, e e, far lighter than 
it need be in the other form of the engine, and but half the 
length. It is forked at the end nearest the cylinder, which 
it thus embraces, and is connected with the cross-head A 
of the piston-rod B, by the connecting rods, d d. 

The peculiarities in this engine, which adapt it to a 
steam-boat will be described in another place. 

108. When a steam-engine is to be set in motion, the 
boiler must first be filled with water, by hand, the fire light- 
ed, and the steam raised to the proper tension. The steam 
and side pipes, the Cylinder, condenser, and air-pump, will 
be full of air, and the whole will be cold. The air must be 
extracted and the engine heated up to the temperature cor- 
responding to the tension of the steam, before it can be set 
to work. This is done by what is technically called blow- 
ing through the engine. The valves are opened and shut 
by hand, and steam is thus introduced to all the parts. As 
steam is lighter than air it will force the air from the cylin- 
der towards the condenser. Hence the air is allowed to 
to escape by a valve contrived for the purpose ; this is 
usually adapted to the condenser, by means of a pipe, 
forming an elbow, and bent vertically upwards. This pipe 
is closed by a conical valve opening upwards. So long 
as air remains in the condenser, and is compressed by the 
steam from above, it is capable of making its way through 
this valve. The completion of the operation is shown by 
its being followed by steam, which, when this valve is 
situated beneath the level of the water in the cold water 
cistern, is known by a slight crackling noise. In the en- 
gine on PI. III. the valve is not thus situated but is adapted 
to a part of the side-pipe in direct communication with 
the condenser. When the steam thus shows itself, the 
injection cock is opened, a condensation of the steam 



CONDENSIiXG ENGINE. 165 

in the condenser takes place almost instantly, and the 
pressure of the steam from the boiler becomes in a short 
time sufficient to put the engine in motion. The eccentric 
is now applied to the crank of the tumbling shaft, and the 
engine becomes self-acting. 



CHAPTER VI. 

GENERAL VIEW OF CONDENSING ENGINES ACTING EX- 
PANSIVELY, OF HIGH-PRESSURE, SINGLE-ACTING, AND 
ATMOSPHERIC ENGINES, PARTICULAR DESCRIPTION OF 
HIGH PRESSURE ENGINES. 

Regulation of steam by the valves of Condensing Engines. — 
Expansive force of steam, supposing the temperature to re- 
main constant. — Expansive force of steam of a given ten- 
sion, and in a given engine, on the same hypothesis. — Ex- 
pansive action of steam of a given tension and constant 
temperature, when the friction and resistance is taken into 
view. — Expansive action at increasing tensions, and with 
temperatures varying according to the law of specific heat. — 
Effects of steam acting expansively, as usually employed. — 
Action of high pressure steam when not condensed. — 
Cases in which high pressure engines are useful. — Recon- 
sideration of the precautions to be used in boilers generating 
high steam. — General view oj the high pressure engine, 
its steam pipes, side pipes, and valves. — Calculation of the 
power of high pressure engines, their working beam, par- 
allel motion, throttle valve, governor, and forcing pump. — 
General view of the single-acting condensing atmospheric 
engines. — Particular description of a high pressure en- 
gine, with a beam, and of long and short slide valves. — 
Particular description of a horizontal high pressure engine. 

109. To set the Double Condensing Engine into motion, 
two of its valves must be opened. One of these admits 



168 CONDENSING ENGINES 

steam from the boiler, to act upon one side of the piston, 
while the other lets the steam from the opposite side, pass, 
into the condenser. These two valves are united so as to 
open and shut together, as are the two, which, alternating 
with them, give motion to the piston in the opposite direc- 
tion. These valves require a certain space of time to 
open to their full extent, and thus the motion of the pis- 
ton in the first instance, and the change at each successive 
alternation are effected gradually. So also the valves are 
permitted to close before the engine has reached the limits 
of its stroke, and thus the shock the engine would sustain, 
and the consequent loss of power are in some measure 
obviated. 

This may, obviously, be effected still more certainly, by 
cutting off the steam at an earlier period of the motion of 
the piston, while the communication with the condenser 
is still left open. 

110. When the steam is thus cut off, it does not lose its 
whole power, nor does it lessen suddenly in force ; for being 
elastic, and acting against a partial vacuum in the conden- 
ser, it will expand, until it either fill the Cylinder, or until 
the friction, and the resistance of the partial vacuum in the 
condenser, become equivalent to its own expansive force. 
Watt, to whom we owe the double condensing engine, was 
the first to remark that advantage might be taken of this, 
to increase the effect of a given quantity of steam. Thus, 
if the Cylinder be but partially filled, and the steam then 
cut off, it will still act expansively, and all the force that it 
continues to exert is so much gained. Were the decrease 
of the temperature, arising from the change in the rela- 
tion of the steam to specific heat, left out of view, the force 
of the expanding steam would decrease in a geometric pro- 



ACTING EXPANSIVELY. 169 

gression, and might be calculated by means of tables of 
hyperbolic logarithms. 

Calculated in this way, the power of a given quantity of 
steam would be increased in the ratios given in the follow- 
ing table. 

Absolute Effects of the Expansive Action of a given quantity 
of Steam, supposing its Temperature to continue constant. 



1 




tI 


Cylinder filled. 


Power of Steam. 




Wholly 


1. 




One-half 


- 1.69 




One-third - - - 


2.10 




One-fourth 


- 2.39 




One-fifth - - - 


2.61 




One-sixth 


- 2.79 




One -seventh 


2.95 




One-eighth 


- 3.08 


, 



111. The advantages of using the steam expansively, are, 
therefore, according to this theory, very remarkable ; but 
to obtain them would require an entire remodelling of the 
engine and the alteration of its proportions. To use the 
same quantity of steam, it would be necessary, that the 
steam pipes, the nozzles, and the Cylinder itself should all 
be increased, in the ratio which the part of the Cylinder 
filled, bears to the whole. If these remain unchanged, the 
consumption of steam, (of equal temperature,) will be les- 
sened in the same ratio inverted, and the force, with which 
the steam would act upon the piston, will have the follow- 
ing ratio. 



22 



170 



CONDENSING ENGINES 



Msolute Effects of Steam acting expansively, in a given 
engine, supposing its temperature to remain constant. 



\ 



r 




■"ii 


Cylinder filled. 


Force. 


Steam expended. 


Wholly 


1.00 


1 


One-half 


0.84 


1 

2 


One-third - - - 


0.70 


X 
3 


One-fourth 


0.57 


1 

4 


One-fifth 


0.52 


1 

5 


One-sixth 


0.46 


1 
6 


One-seventh 


0.42 


1 


One-eighth 


0.39 


1 
¥ 



These calculations are, as has been stated, made upon 
the hypothesis, that the temperature continues invariable, 
which is far from being the case ; " for steam, like all other 
substances, has its capacity for specific heat increased 
during its expansion, and its temperature and consequent 
elasticity are diminished. 



112. It must next be taken into view, that the absolute 
power of the steam is opposed by a constant resistance, in 
the form of friction and imperfection in the vacuum of the 
condenser, which amounts to 7ilbs. per square inch, or 
half an atmosphere ; for steam, as has been seen, act- 
ing with an expansive force of 17i^lbs. per square inch, 
is only capable of overcoming a resistance equivalent 
to lOlbs. Hence, in an engine working at low pres- 
sure, the advantage gained by making it act expansively, 
would cease, if the steam were cut off earlier than at 
half the stroke, for at //„ the resistances would be equal 
to the expansive force, even if the temperature remained 
constant, which, as we have seen, it does not. The mo- 
tion might indeed be kept up for a time by the fly-wheel, 
hut even then, without taking into view the irregularities 
that would ensue, the effective action would diminish most 
rapidly, as will appear from the following table. 



ACTING EXPANSIVELY. 171 

Effects of Steam acting expansively upon a given engine, 
taking into account the friction, but supposing the tempera- 
ture to remain constant. 



r — 




-t1 


Cylinder filled with Steam 


Mean 


effective Force. 


of 171-21bs. 






Wholly 


_ - - 


1.00 


One-half 


... 


0.72 


One-third 


... 


0.48 


One-fourth 


... 


0.26 


One-fifth - 


... 


0.17 


One-sixth 


- - - 


0.06 


One-seventh 


- 


0.00 


_ 







We therefore conceive ourselves warranted in the con- 
clusion, that v^hen an engine acts expansively, the steam 
should never be permitted to expand itself, to more than 
twice the bulk it occupies under the atmospheric pressure. 

Working at low pressure, to produce an equal effect, 
the engine should be nearly one-half larger in its capacity, 
and the expense of fuel would be three-fourths of what it 
would be, if the steam were employed in the usual manner. 
Unless, therefore, in cases where fuel is extremely scarce, 
there is probably no real advantage to be gained, in making 
low pressure steam act expansively. 

113. There is another point of view in which the ex- 
pansive action of steam may be investigated, for the steam 
may be used at an increased pressure. If it have an 
expansive force of an atmosphere and a half, it would, if 
cut of at one-third of the stroke, expand, in filling the 
Cylinder, to the assumed limit of pressure, of half an at- 
mosphere. The original effective force, after allowing for 
resistance, would be 151bs. per square inch, and the mean 
action would be two-thirds of that amount, or lOlbs. per 
inch during the whole stroke. Hence the engine would 
now work up to its nominal power. 



172 CONDENSING ENGINES 

Steam, under a pressure of li atmospheres, has, if we 
leave out of view the temperature, a density one and a 
half times as great, as under atmospheric pressure simply, 
hence to fill one-third of the Cylinder would require the 
evaporation of as much water as would fill half the cylin- 
der with steam of 212". An engine, therefore, acting ex- 
pansively with steam of the elasticity of 1|^ atmospheres, 
would, on this hypothesis, do the same work as when acting 
in the common manner, and consume hut half the quantity 
of fuel. For as the sum of the latent and sensible heat is 
the same, both in high and low steam, the quantity of water 
converted into steam is the same, whatever be its tempera- 
ture. 

Let us next suppose the steam to have an elastic force 
equal to two atmospheres. It might, on the same hypo- 
thesis, expand to four times its original bulk, before its 
elasticity became less than half an atmosphere. Hence it 
might be cut ofi" at one-fourth of the stroke. 

Its original effective force, after deducting the constant 
resistance, will be 22^1bs. per square inch, and it will act 
with a mean force of y^^ of that amount or upwards of 
12 Ubs Hence the engine will, under such circumstances, 
work with one-fourth more than the power at- which it 
would be estimated, according to the common rule. 

The steam would in this case also fill half the cylinder, 
before it reached the density of steam of 212% and hence 
the quantity of water used, and fuel expended would be the 
same as in the former. And, in all cases, where the limit of 
the expansion of the steam is an elasticity equal to half an 
atmosphere, the quantity of water evaporated and fuel ex- 
pended would be constant. But the efiective power would 
go on increasing with the elasticity of the steam, accord- 
ing to the following table. 



ACTING EXPANSIVELY. 



173 



Relative power of the same engine acting in the ordinary man- 
ner, or expansively. The temperature being supposed not 
to vary on expansion. 



r ■ 








Steam in 
Atmospheres. 


Cylinder 
filled. 


Fuel 
Expended. 


Effective 
Force. 




wholly 

X 


1 

0.5 


10 
10 


2 


I 

4 


0.5 


12i 


2i 
3 


I 

T 
1 

■g- 


0.5 
0.5 


15f 

18 


3f 


1 


0.5 


19 


4 


1 

IS 


0.5 


20 



114. In order to cut off the steam, a valve of the figure 
of a throttle valve is placed in the steam pipe. A weight, 
or strong spring closes it and keeps it shut, except when 
the one is lifted, or the other forced back, by the action of 
the engine. This is usually performed by placing two 
teeth or cams, of proper form and size, upon the axis of the 
crank. A plan of this kind may be seen on PI. IV. Fig. 6. 
Where c is the axis of the crank, a and h two cams, or teeth, 
that act upon the spring g d, which is connected with the 
handle c f of the expansion valve, by the rod d e. i^ is a 
portion of the steam pipe. 



115. The estimate that has been given of the powers of 
steam acting expansively, is, as has been seen, formed 
upon the hypothesis that it expands to bulks that are in- 
versely as the pressures. This is not the case, in conse- 
quence of the change of temperature, that the very act of 
expansion produces. Thus steam of a tension equivalent 
to half an atmosphere, has a temperature of 180" and a 



174 CONDENSING ENGINES 

density of 0.00032, while, with a tension of 2, 3, and 4 
atmospheres, it has the following densities. 

2 Atmospheres 0,00111 

3 do. 0.00160 

4 do. - - - - - - 0.00210 

Steam of 

2 Atmospheres expanding to 4 times its bulk has 

a density of - - - 0.00028 

3 do. to 6 times its bulk, - - 0.00027 

4 do. to 8 times its bulk, - - 0.00026 

In a vessel which would neither give nor abstract heat, 
the tension and temperatures would be diminished, in the 
three several cases, in the ratios of |f or -|, |f, and |f or 
if. But in an expansive engine, the cylinder may be 
readily kept up to the temperature of the steam, before it 
begins to expand, and the steam in expanding will derive 
heat from it. The method, which is occasionally adopted in 
a low pressure engine, of enclosing the cylinder in an outer 
case, called a jacket, will be far more beneficial in an engine 
acting expansively, and the diminution in tension, arising 
from diminished density, will be counteracted by increased 
heat. This, however, will be attended with a loss of heat 
in the surrounding steam, and will require the capacity of 
the boiler to be increased in proportion. It is, therefore, to 
be taken into view, that the comparison of engines acting 
expansively as given upon page 173, is not absolutely true, 
but that in order to make it so, the fire surface of the boiler 
should be increased ith at the pressure of two atmospheres, 
and ith at the pressure of four, and the safety valve loaded 
with additional weight in the same proportion. The ex- 
penditure of fuel will also be increased in the same de- 
gree. The advantage derived from making engines act 
expansively, are still great, notwithstanding this increase 






.% 



ACTING EXPANSIVELY. 



175 



in the expenditure of fuel, for an engine receiving steam of 
the tension of 4.| atmospheres, cut off at ith of the stroke 
will do twice as much work, as one receiving low steam, 
with but six-tenths of the fuel it expends. If we correct 
our previous calculations, upon these principles, the results 
will be as follows, which will give the actual effect which 
may be produced by the same engine, acting at low pressure 
or expansively, with different loads on the safety valve. 

Relative powers of the same engine, acting at loio pressure or 
expansively, the change in the relations of the expanding 
steam to temperature being taken into account. 



r 






— 11 


Load on the 


Cylinder 


Fuel 


Effective 


Safety Valve. 


filled. 


Expended. 


Force. 


31bs. 


wholly 


1 


10 


lOlbs. 


I 

3 


0.55 


10 


191bs. 


1 
4 


0.56 


12i 


27lbs. 


1 
5 


0.57 


15^ 


361bs. 


1 


0.58 


18 


461bs. 


1 

T 


0.59 


19 


571bs. 


1 
S 


0.60 


20 

i 
_j 



High as even this reduced estimate may appear, of the 
power of engines acting expansively, it is considerably less 
than would be deduced from the original investigations of 
Watt and Robinson. It differs still more remarkably from 
the views of Woolf, who states, that steam, under a pres- 
sure of 5lbs. in addition to an atmosphere, acquires the 
power of expanding itself to four times its original bulk, 
without ceasing to be equal in elasticity to the atmosphere; 
and generated under a pressure of lOlbs., it will expand 
ten times and still retain the force of one atmosphere. 
These views are, however, wholly erroneous, as they are in 
direct contradiction to the nature of steam, and the rela- 



176 CONDENSING ENGINES 

tions its tension bears to pressure and temperature. Our 
own moderate estimates we consider to be far nearer the 
truth, and as likely to be worthy of reliance. Still, how- 
ever, it could have been wished, that we could have obtain- 
ed experimental facts to adduce, in corroboration of these 
theoretic calculations. 

The subject is therefore submitted, in this form, to the 
public, in the hope that the advantages it promises may 
lead to an experimental inquiry. Several engines, in the 
steam-boats on the North-River, act expansively, and with 
obvious benefit, but in no one is the principle carried to 
such an extent as to exhibit all its excellencies. 

From what has been said, it will be obvious, that very 
great advantages may be gained by making engines act ex- 
pansively. And the advantage is so much the greater, as 
from the moment that this system is adopted, it becomes 
unnecessary to change the size and figure of the boiler in 
any great degree, nor is there any material change neces- 
sary in the area of the steam passages, so that the same 
engine may be made to work, from its power according to 
the usual estimate, up to double that force^ and shall use no 
more than six-tenths of the fuel consumed, when the steam 
is employed at ordinary low pressures, and not cut off. 

116. The principle, valuable as it appears from the fore- 
going calculations to be, has been but sparingly introduced 
into practice ; never indeed, as far as we have been able 
to learn with steam of a pressure of more than li atmos- 
pheres. At this limit the advantage of the method is hard- 
ly developed, inasmuch as the power of the engine is not 
increased, although there is no doubt a great saving of fuel. 

Working with steam of the tension of 1 1 atmospheres, it 
is customary to cut off the steam at half stroke. The 
mean effective pressure calculated upon the principles on 



ACTING EXPANSIVELY. 177 

page 173, becomes 12ilbs. per square inch, and the quantities 
of water evoporated and fuel consumed, three-fourths of 
what are expended, when working at full stroke, with steam 
of one atmosphere. In this case, it will be necessary to in- 
crease the areas of the valves beyond the proportion given 
in the description of the condensing engine on page 147. 

117. When steam of high pressure is used to propel en- 
gines, it is more customary to make it act without the aid 
of a condenser, and consequently in opposition to the whole 
pressure of an atmosphere. 

The engine, in this case, becomes much more simple 
inasmuch as the condenser and air-pump may be dispensed 
with, as well as the cold and hot water pumps ; but for the 
latter is substituted a forcing pump to feed the boiler, and 
in most cases a common pump will be needed, to raise the 
supply. The cold water cistern and the water for conden- 
sation are no longer necessary, and thus a very great weight 
may be saved, which in some cases is of great importance. 

In estimating the resistances which the action of the 
steam meets with, it is to be considered, that the imperfec- 
tion of the vacuum of a condensing engine merges in the 
pressure of the atmosphere, in one where the steam is not 
condensed ; and that thus the resistances, which, in the 
former, were estimated at 7|lbs. per square inch, may be 
diminished, as well as by the power required to work the 
air and cold-water pumps. The resistances, other than 
the pressure of the atmosphere, need not therefore be taken 
at more than 51bs. per square inch, which, added to the 
pressure of the atmosphere, makes a constant resistance to 
the action of the steam, in a high pressure engine of 201bs. 
per square inch. Hence, steam of an expansive force of 
two atmospheres will work in a given cylinder with the 
same force that steam of 17|lbs. would work in a con- 
densing engine. But steam under a pressure of two at- 

23 



178 HIGH PRESSURE ENGINES. 

mospheres has rather less than two-thirds of the density of 
steam of 17|lbs. per inch ; and hence it would require 
more than li times as much water to be evaporated in order 
to fill the cylinder, and l^ times as much fuel. In this 
case, therefore, there would be a loss of 50 per cent, in 
using a high pressure engine. 

If the steam had a pressure of 2i atmospheres, its effect- 
ive force would be 17ilbs. per square inch, or would bear, 
to that in a low pressure condensing engine, the ratio of 7 
to 4. But, to fill the Cylinder with steam of corresponding 
density, would require nearly twice as much fuel. 

At a pressure of three atmospheres the effective power 
of the steam becomes 251bs. per square inch, or bears to 
that of a low pressure engine the ratio of 5:2. To fill the 
cylinder with steam of this density, requires fuel in about 
the same ratio, and hence, at this limit, the power of high 
and low pressure engines, consuming the same quantity of 
fuel, becomes nearly equal. 

With four atmospheres of steam, the effective pressure 
becomes 401bs., the consumption of fuel is about three to 
one, and here the high pressure engine has an advantage in 
the ratio of four to three. 

At five atmospheres, the effective pressure is 551bs. per 
inch, the ratio of water evaporated or fuel consumed as 
3fths to 1. Arranging these and similar calculations in a 
table, we have as follows : 



HIGH PRESSURE EJVGINES. 



179 



Effects of High Pressure Steam to work Engines. 



i 



Pressure in 


Fuel in the 


Force in the 


Force with the 


Atmospheres. 


same Engine. 


same Engine. 


same Fuel. 


2 


1^ 


1 


0.75 


2i 


2 


1.75 


0.875 


3 


n 


2.5 


1.000 


4 


3 


4 


1.333 


5 


H 


5.5 


1.46 


6 


H 


7 


1.55 


10 


7 


13 


1.86 


20 


14 


28 


2.00 


30 


20 


43 


2.15 


40 


26 


58 


2.23 



118. It thus appears/that the useful effect of high pressure 
engines, increases far more slowly than the increase of the 
elastic force of the steam. This arises from the fact, that 
the density of steam increases nearly as fast as the pressure 
under which it is generated. Did both increase in the same 
ratio, there would be nothing gained by the use of high 
steam. A high pressure engine is, therefore, far inferior 
in power, to one in which the steam acts expansively, and 
is subsequently condensed ; as will appear from a com- 
parison of the preceding table with that on page 173. 

There are, however, cases in which the high pressure 
engine is preferable to any other. Thus, when water is 
scarce, the high pressure engine dispenses with the use of 
that employed in condensing the steam, which, as we have 
seen, is 22 times as great as that which is evaporated 
from the boiler. The weight of the air-pump and conden- 
ser, of the cold and hot water cisterns, as well as of the 
water they contain, are all saved. Hence, where locomo- 
tion is important, as where steam is employed to propel 
carriages upon railways, high pressure engines can alone 
be used. These engines are also much simpler in their 



180 HIGH PRESSURE ENGINES. 

construction, being composed of fewer parts ; and they 
occupy far less room than condensing engines, whether the 
latter act expansively or not. 

119. Whether an engine be constructed to receive the 
most important advantages from the expansion of the steam, 
or be a simple high pressure engine, in which the steam, 
after it has caused the piston to perform its motion, is per- 
mitted to escape into the open air, the boiler must be so 
constructed as to contain and generate steam of high elastic 
force. Common high pressure engines work usually with 
steam of from five to six atmospheres, and there is no 
doubt that expansive engines might be constructed in such 
a manner as to be worked advantageously, with a little less 
than five atmospheres. The load of the safety valve is at 
this latter limit 571bs., while to contain steam of six atmos- 
pheres, requires a load of 751bs. per square inch. It re- 
mains to inquire, how far it may be consistent with safety, 
to employ steam of such expansive force ] The principles 
on which the strength of boilers depends, have been fully 
illustrated in Chapter III. From what has there been stated, 
it will appear that the cylinder is the best form for boilers 
and that a boiler of this shape, and of small diameter, may 
be made to resist the regular pressure of far more than six 
atmospheres ; that by diminishing the diameter of the 
cylinder the strength is increased in the inverse ratio of the 
squares of the diameters ; and that by a reduction in this 
dimension, any required strength may be obtained. The 
application of the Hydrostatic press furnishes a proof, in 
the first instance, of the cohesive force of the material and 
the joints, to resist any given pressure, and the proof may 
be finally completed, by subjecting the boiler to the action 
of steam of more elastic force than it is ever likely to be 
compelled to bear in practice. The steam-guage will ena- 



HIGH PRESSURE ENGINES. 181 

ble the engineer to know that the pressure is kept below 
the desired limit, and the safety valve opens as soon as 
that limit is reached. In case of a deficiency in the supply 
of water, or obstruction in the feeding apparatus, a thermo- 
meter will shew the increased heat that is the consequence, 
and plates of fusible metal will melt as soon as a safe limit 
of heat is passed. A self-acting feeding apparatus will 
generally furnish a regular supply, for the failure of which 
the last mentioned apparatus affords a safeguard. Regis- 
ters and dampers will allow the fire to be moderated, and 
almost extinguished, whenever it becomes necessary. Next, 
the tendency of solid matter to collect and be deposited on 
the bottom of the boiler, may be lessened by mixing vege- 
table feculae with the water, but careful cleansing will be 
required, at proper intervals, to obviate all danger from this 
cause. If an engine must be in constant operation, it 
ought never to have less than two boilers, one of which 
can be employed, while the other is under repair ; and in 
all cases of constant employment, there should be one 
boiler more than is necessary to supply the engine. If the 
work be of such a nature, that the persons employed about 
the engine may have a temptation to increase the force of 
the steam, beyond the proper degree, there should be two 
safety valves, one of which should be beyond their control. 

No one of these precautions should be omitted when 
high steam is used, unless they are impossible from circum- 
stances. In locomotive engines, and in steam-boats, spare 
boilers cannot be introduced ; the necessity for them, may, 
however, be done away, by prescribing stated periods of 
inactivity, when the boilers may be cleansed. 

With these precautions, we do not hesitate to say, that 
boilers in which high steam is generated may be rendered 
as little liable to accident as low pressure boilers ; and 
indeed, the more common cause of explosion, namely, 



182 HIGH PRESSURE ENGINES. 

the exposure of the metallic flues, or the sides of boilers, 
to the fire, when not covered with water, is as likely to 
affect low pressure boilers as high. Of the two fatal ex- 
plosions that have occurred in the harbour of New-York, 
one was a copper boiler containing low, the other an iron 
one containing high steam. But although, with proper 
precautions, high pressure boilers may be rendered as little 
liable to burst, as those planned for generating high steam ; 
the explosions of the latter, when they do take place, are 
more likely to produce dangerous consequences than the 
former. We have ourselves been in two instances in steam- 
boats when low pressure boilers have given way, and the 
fact was only known by the stopping of the engine. This 
will always be the case when they give way under the ordi- 
nary pressure of the steam, for supposing the safety valve 
to be loaded with 31bs. per inch, the escape of no more 
than a fifth part of the steam will restore the equilibrium 
between the outer and inner sides of the boiler. Even if 
the boiler burst at the limit of its proof, the quantity of 
steam that can escape is little more than the half of that 
it contains in it. 

In boilers containing steam of four or five atmospheres, 
a vent will allow the steam to expand itself to four or five 
times its original bulk, even when it takes place under 
ordinary circumstances ; while if it occur at the limit of the 
proof, in consequence of the safety valve ceasing to act, the 
steam may have tendency to expand itself to ten or twelve 
times its original bulk, and even in the former case, the ex- 
plosion may be dangerous. In a low pressure engine, any 
dangerous explosion then that can occur, grows out of the 
subsidence of the water below its proper level, and the very 
weakness of its material is a cause of safety. While in a 
high pressure boiler, the same risk is incurred, and in addi- 



HIGH PRESSURE ENGINES. 183 

tion a giving way even under the usual state of the steam, 
may sometimes be dangerous. 

A boiler, however, that has been properly proved, and is 
examined at regular stated periods, cannot well burst, ex- 
cept by the clogging of its safety valve, or by the uncover- 
ing of its sides and flues. The former accident may be con- 
sidered as hardly within the limit of possibility, if the 
guages of the engine are in order ; and as both species of 
boiler are equally liable to the latter, we conceive that it 
may be considered as certain, that no more risk is now in- 
curred, by using high pressure steam, than by using low. 

In expressing this opinion, it must be repeated that all 
the safety apparatus we have spoken of must be applied to 
the high pressure boiler, and that in steam-boats and locomo- 
tive engines there be an additional safety valve, beyond the 
control of any person, on board the former, or entrusted 
with the management of the latter. 

120. Such being our views of the possibility of using 
high steam with safety, we confidently anticipate, that, 
cylindrical boilers, generating high pressure steam, will 
supersede all others. These will be apphed in most cases 
to condensing engines acting expansively ; but where sav- 
ing of weight, or of room, and even of original cost is an 
object; in locomotive carriages ; in boats navigating shallow 
rivers; and wherever water is scarce, high pressure engines 
will be employed. Being less complex, they will also be 
preferred, wherever good workmen to perform the repairs, 
or intelligent engineers are not to be obtained. 

121. The parts of a high pressure engine are the 
following : — 

A steam-pipe through which the steam passes from the 
boiler ; the area of this is calculated upon the principles 
laid down on page 102. 



184 HIGH PRESSURE ENGINES. 

Side pipes connected at one extremity with the steam- 
pipe, and at the other with the open air. In these are 
situated the valves which admit steam alternately to the 
opposite sides of the piston, or permit its escape. The 
original form of the valve was a cock with two passages 
and four openings, proposed at first by Leupold, and adopt- 
ed both by Trevithick and Evans. This valve is represent- 
ed on the opposite page. M J^Tis the cylinder of the en- 
gine ; a b the side-pipe, in the middle of which is a conical 
socket, to which is adapted a frustum of a cone, with two 
passages d e, and consequently four openings ; c is the steam 
pipe, and / g the waste-pipe, or in a condensing engine the 
communication with the condenser ; h is the lever by which 
the valve is turned through a quadrant, at each stroke of the 
piston; and i is the other position of the lever. The steam 
in the position of the valve that is represented on the draw- 
ing, flows from the pipe c through the passage e into the 
lower part of the side pipe b and thence enters beneath the 
piston ; while the steam above the piston flows out at a 
through the passage d into the pipe / g ; in the other posi- 
tion of the valve the motion of the steam is obviously 
reversed. 



HIGH PRESSURE ENGINES. 



185 




For this, in some recent American Engines, has been 
substituted a short slide valve, which has been found by ex- 
perience to be more advantageous. This valve is worked 
by an Eccentric placed upon the axis of the crank ; a con- 
venient mode of doing this is represented upon PI. IV. at 
Fig. 3. where, 

A is the axis of the crank ; 

B the circular plate, a a a a triangular frame ; 

h rod and adjusting screw ; 

c handle, d arm of tumbling shaft ; 

24 



186 HIGH PRESSURE ENGINES. 

e axis of tumbling shaft ; 

/ / spindle of slide valve ; 

g g steam chest ; 

H steam pipe ; 

I eduction pipe ; 

k k bottom of cylinder, on which is cast a piece 1 1 con- 
taining one of the steam passages. 

A plan, and section of this valve are represented on PL 
II. Fig. 5, and will be described hereafter. 

The Cylinder resembles in form that of a condensing 
engine, fitted with a piston, and piston-rod passing steam- 
tight, through the cover of the engine. 

122. The power of the Engine is calculated by taking 
the continued product of: the effective pressure of the 
steam per square inch in lbs., the area of the piston, the 
length of stroke in feet, and the number of strokes per 
minute ; which product divided by 33000 gives the number 
of horse powers. The effective pressure of the steam is 
201bs. less than its absolute expansive force, or 51bs. less 
per inch than the load of the safety valve. It is, however, 
usually calculated at two-thirds of the pressure of the 
steam, which is the true amount when the steam is equi- 
valent to 4 atmospheres, or the safety valve is loaded with 
451bs. per square inch. 

123. The action of the piston may be conveyed to the 
working points of the engine in the same manner as in the 
condensing engine. All, therefore, that has been said on 
pages 119 et seq., is applicable here. So also, when the 
machinery requires regulation, a fly-wheel is adapted to the 
crank, and where the work must be performed at a con- 
stant velocity, a Governor, acting upon a throttle-valve, is 
adapted. 



ATMOSPHERIC ENGINE. 187 

A parallel motion for a high pressure engine is represent- 
ed on PL IV. Fig. 1. In this, 

c d represents the lever-beam ; 

b the piston-rod; 

c and d the pivots of the parallel motion ; 

e the pivot to vv^hich the piston rod is attached ; 

g g B- part of a fixed frame that bears the pivot h of the 
radius bar ; 

c e and dfQ,Ye the straps; 

hf the radius bar ; 

e f the parallel bar. 

The governor of a high pressure engine is represented on 
the same plate at Fig. 2 ; a and b are the two bevel wheels ; 

C d the axis of the governor ; 

e e spherical weights, suspended by rods from joints on a 
fixed collar/; 

o- is a collar sliding on the axis c d, by the motion of the 
bars g h, g h; 

H is a circular arc forming a loop at each end, in which 
the bars f h, f h play ; 

g h k IS a, lever moving on the pivot k ; 

/ Z a connecting rod that unites the end I of the lever to 
the handle or lever of the throttle valve. 

124. The forcing pump that feeds the boiler, and the 
lift-pump that supplies the water which the former injects, 
are worked by rods from the lever beam, when the engine 
has one. In other cases, motions are taken off from the 
piston-rod in such a way as to answer the same purpose. 

125. The high pressure engine is thus fitted to subserve 
all the objects that can be fulfilled by the double-acting 
condensing engine. There are, however, engines which 
are not suited to produce more than a reciprocating ac- 



188 ATMOSPHERIC ENGINE. 

tion, and which were of older date, although of less value, 
being applicable to but a few purposes. Such is the siij- 
gle-acting condensing engine. In this engine ; the lever- 
beam is loaded with a weight, at the end opposite to that 
to which the piston is attached, and the latter rests when 
the engine is not in action, at the top of the Cylinder. 
The Cylinder and steam passages are then filled with 
steam ; a communication is now opened, from the lower 
side of the piston, with the condenser, and the pressure of 
the steam, on the upper side, forces the piston down to 
the bottom of the Cylinder ; the steam and condensing 
valves are next closed, and the third valve, which forms 
a communication between the opposite sides of the piston, 
is opened ; there being now no resistance to the motion 
of the piston, other than the friction, the weight at the 
opposite end of the beam again preponderates, and the pis- 
ton is drawn back to its pristire position, the steam flowing 
through the open valve and steam pipe, from the upper to 
the lower side of the piston. 

In this engine the steam acts only during the downward 
stroke of the p -i^n, and during its return no force is ex- 
erted upon the piston. The effort is, therefore, directed 
to raise a weight, which may, in its descent, perform a work 
of such nature as is suited to this peculiar species of alter- 
nating motion. The raising of water, by a forcing pump, is 
the most usual purpose to which such an engine is applied. 

A parallel motion is unnecessary in this engine, and the 
piston-rod is connected with the beam by a chain, that ap- 
plies itself to a circular arc on the end of the beam. The 
pump-rod, loaded with a weight, is attached in a similar 
manner to the opposite end of the beam. 

The air-pump, the cold and hot water pumps, are at- 
tached to rods worked by the beam. 

The power of this engine being exerted during one mo- 



HIGH PRESSURE ENGINES. 189 

tion of the piston only, is obviously no more than half of 
that of a double-acting condensing engine of the same 
dimensions. It is besides applicable to but very few pur- 
poses : and as the same purposes may be accomplished by 
a double-acting condensing engine of half the size, this 
form has gradually fallen into disuse. It was, however, at 
one time much in use for draining the water of mines, and 
raising that fluid for the supply of cities. 

126. At a still earlier period in the history of the Steam 
Engine, an engine was employed, in which the air of the 
atmosphere acting upon the piston was the prime mover. 
The vacuum on the lower side of the piston, is caused by a 
condensation, effected in the cylinder itself. This engine 
is, for the reasons mentioned on page 117, far inferior to 
those in which a separate condenser is employed. It is 
also inferior in effect to an engine in which steam is the 
moving power, for the latter is always made to act with a 
force a little superior to simple atmospheric pressure. 

127. The two forms of Engine last mentioned are now 
obsolete ; and the expansive engine does not differ in form 
from the double-acting condensing engine : we shall there- 
fore, res'rict ourselves to the description of thehigh pressure 
engine, and leave the detail of the others, until we treat of 
the history of the invention. 

On PL V. is represented a high pressure engine of 30 
horse power, manufactured by the West Point Foundry 
Association. 

A is the cylinder, the stroke of whose piston is about 
three and a half times the diameter. It stands upon a rec- 
tangular vessel I, through which the waste steam passes, 
heating water that is raised to it by a Uft pump, not repre- 
sented in the plate. 



190 HIGH PRESSURE ENGINES. 

The piston-rod 6, is seen only in the end view, and is 
hidden in the other, by the slides c c, in which its cross- 
head moves. This rod is attached to the lever-beam d, by 
straps a a, whose length from centre to centre is half the 
stroke of the piston-rod. 

D is the lever-beam, the length of each of whose arms 
is rather more than three times as much as the stroke of 
the engine. 

E the Connecting-rod or Shackle-bar. 

F, the Crank. 

G G, the Fly-wheel. 

H, a reservoir of water, through which the waste steam 
passes by a pipe, until it finally escapes by the tube r r. 

ff, is the eccentric, which moves the tumbling shaft k, 
to which is attached, by connectiiig rods, a cross-head I, 
which gives motion to the slide valve contained in the 
side pipe b. 

g g, is an endless chain passing over drums, one on the axis 
of the crank, the other on that of the vertical bevel-wheel. 

h, are two bevel-wheels that give motion to the axis of 
the governor k. 

While the balls of the governor diverge, they raise one 
end of the lever i, the opposite end is pressed down and 
closes the throttle valve, situated at c, in the steam pipe. 

d is the rod of the forcing pump that conveys water from 
the reservoir h, to the boiler 

A section of the Cylinder of this engine, and of its slide 
valve, is represented on PL II. Fig. 4. 

/, lower passage for the steam. 

c, upper passage for do. 

h I, openings in the sliding pipe, adapting themselves al- 
ternately to the passages e, and/. 

g, third opening in th • s c am pipe, represented as apply- 
ing itself to the eduction passage m. 



HIGH PRESSURE ENGINES. 191 

m, eduction passage to which the openings I and g apply 
themselves alternately. 

i, i, interior of the side pipe, in which the slide is work- 
ed by the spindle, 

kf spindle, connected by rods with the eccentric. 

Another slide valve for a high pressure engine is repre- 
sented in its connexion with the Cylinder at Fig, 5, on 
the same plate. 

a, b, c, d, is a rectangular bar of cast-iron, called the 
steam-chest ; it is constantly receiving steam from the 
boiler. The lower side of this has three openings, repre- 
sented 3it g, Cy /, in the ground plan. 

Within the steam-chest, is a septum g, being a cup, or 
trough of a rectangular shape, whose open face is down- 
wards, and is ground to apply itself closely to the lower 
plate of the steam-chest, against which it is firmly pressed 
by the steam. 

This septum is of such a size as to cover two of the 
openings of the plate, and to exclude the third. Hence, 
one or other of the lateral openings, always communicates 
with the middle opening, through the septum, while the 
remaining one receives steam from the steam-chest. This 
septum is drawn backwards and forwards by the spindle A, 
which is worked by an eccentric. 

The central opening c, corresponds to the eduction pipe 
by which steam escapes, the other two communicate, one 
with the upper part of the Cylinder, the other with the 
lower, and in the varying positions of the sliding septum, 
steam is alternately admitted from the steam-chest and 
allowed to escape by the eduction pipe through these aper- 
tures. 

A Horizontal high pressure Engine, manufactured by the 
West Point Foundry, is shewn on PI. VI., together with its 
two cylindrical boilers. 



192 HIGH PRESSURE ENGINES. 

Jly ashpit. 

B, B, furnace doors. 

C, "C, boilers. 

D, cylinder. 

E, piston-rod. 

F, connecting rod. 

G, G, G, fly wheel. 
H, governor. 

/, reservoir of cold water. 

K, forcing pump. 

L, cistern of water to be heated by waste steam. 

a, pipe forming communication between the water in the 
two boilers. 

b, b, b, steam pipe. 

c, safety valve. 

d, lever and weight of safety valve. 

c, pipe for waste steam from safety valve. 

/, pipe for waste steam after it has passed the valves and 
been used in the cylinders. 

g, steam chest containing slide valve. 

h, pipe by which the cold water is conveyed to the reser- 
voir /. 

i, pipe by which water passes from the reservoir to the 
cold water cistern. 

k, continuation of pipe /. 

Z, /, I, parallel motion for vertical forcing pump. 

n, n, n, eccentric. 

0, tumbling shaft. 

A section of the cylinder of this engine, with its side 
pipe, is to be found on PI. II. Fig. 6th. 

It has been objected to the horizontal form of Steam 
Engines, that the packing wears unequally, being first ab- 
raded on the lower side of the piston, and that the Cylin- 
der itself must finally be worn into an elliptical shape. 



HIGH PRESSURE ENGINE. 193 

With proper precautions in the use, however, no practical 
difficulty need arise. Engines of this form have advanta- 
ges, in various cases, that shall hereafter be ennumerated, 
particularly in their application to steam-boats. 

High pressure engines are also occasionally constructed 
without the lever beam ; the form and distribution of the 
parts resemble, in this case, the condensing engine figured 
on PI. VII. 



25 



CHAPTER VII. 

EARLY HISTORY OP THE STEAM ENGINE. 

introduction. — Statue of Memnon. — Hero of Alexandria, — 
Eolipyle. — Anthemius and Zeno. — Cardan.—Mathesius.'— 
Baptista de Porta. — De Causs. — Brancas. — Wilkins and 
Kircher. — JWarquis of Worcester. — Hautefeuille. — Papin^s 
first plan. — Savary. — Papin's Engine for the Elector of 
Hesse. — Jfewcomen and Cawley. — Potter^s Scoggan. — 
Btighton's Hand- Gear. — Smeaton. — Leupold, 

128. The description of the steam engine,, given in the 
previous chapters, has been limited to the three more im- 
portant varieties : the double-acting condensing engine 
impelled by low steam ; the double engine acting expan- 
sively ; the high pressure engine. These alone are in 
general actual use, and the consideration of their theory is 
all that is directly valuable, to the maker, or user of steam 
engines. The various other forms that the engine has 
assumed, in its progress from rude beginnings to its present 
improved state, the several projects that have been brought 
forward, and successively abandoned, may be best treated 
of in the historical form. In this manner also, may the 
relative merit, of the inventors and improvers, be best set 
forth. 

. The steam engine, as it is the most powerful agent by 
which the power of man has been extended, so also has it 
employed the labour, ingenuity, and talent of more indi- 
viduals than any other human invention. 



196 



HISTORY OF THE 



To give the true history of the steam engine, as indeed 
of most of the discoveries that have conferred important 
benefits on mankind, would be, in fact, to enter into the 
annals of nearly all the arts and sciences. Instruments have 
been frequently contrived, and principles stated, for which the 
world was not at the time prepared. Centuries sometimes 
elapse, before the period arrives, at which the wants of 
society call for their application, or the intelligence of the 
age can appreciate their merit. Then some more fortu- 
nate genius recalls the forgotten plan from oblivion, or 
unconscious of the labours of his predecessors, derives 
from his own resources, inventions, not perhaps more meri- 
torious than theirs in the abstract, but suited to the con- 
dition and wants of his cotemporaries. To the last then 
is the world really indebted, and to him is the gratitude due. 
His predecessors may have even gone beyond him in actual 
progress, his cotemporaries may have been upon the eve 
of the same discovery, and may have been so far advanced, 
that a few years, months, or even days would have placed 
them by his side. But the good fortune, and it may per- 
haps be little more, of him who first reaches the useful 
result, must eclipse the merit of all others. Priority in the 
application of an invention to practical purposes, if asso- 
ciated with originality, or even with the calling up of for- 
gotten projects, that were impracticable or useless at the 
moment of their first conception, is the point on which a 
claim to high distinction in the annals of the useful arts 
must depend. 

In the history of the steam engine then, a few names 
stand prominent, in consequence of the immediate advan- 
tages to the world with which their labours were followed. 
Savary who first successfully substituted steam for the 
labour of animals; Newcomen, who first succeeded in 
applying it to move a solid body, through whose interven- 



STEAM ENGINE. 197 

tion the work might be performed ; Watt who called in 
physical science, to discover and remedy the defects of his 
predecessors, and made the steam-engine an instrument 
of universal application ; Fulton who performed the first 
successful voyage by the impulse of steam ; and Evans 
and Trevithick, who cotemporaneously gave to the engine 
such a form as suited it for locomotion on land, and ascer- 
tained that such locomotion was practicable. 

It is necessary, before we enter into the history, to par- 
ticularize these authors of the great steps the steam engine 
has made, in principle, or in application ; for the more mi- 
nute our inquiries become, the more will the real, and 
vastly superior merit of these parties, seem to descend to 
the level of others, whose ingenuity, either formed the basis 
of the strides made by those we have named ; who had 
previously nearly reached the same results ; or were on 
the very eve of attaining them. Thus Savary and Newco- 
men united, did but little more than the Marquis of Wor- 
cester had done before them, but had not applied to pur- 
poses of real utility ; Watt found a competitor in the person 
of Gainsborough ; and but a few weeks would have placed 
Stevens on the very eminence where Fulton now stands. 

The fitness of the time at which these several inventors 
succeeded in their projects, if it be rather to be ascribed 
to good fortune than to pre-eminent merit, tends still more 
than any other cause to separate them from their competi- 
tors. Had the mines of Cornwall been still wrought near 
the surface, Savary or Newcomen would hardly have found 
a vent for their engines. Had the manufactures of England 
been wanting in labour-saving machinery, the double-acting 
engine of Watt would have been suited to no useful appli- 
cation ; a very few years earlier than the voyage of Fulton, 
the Hudson could not have furnished trade or travel to 



198 HISTORY OF THE STEAM ENGINE. 

support a steam-boat, and the Mississippi was in possession 
of dispersed hordes of savages. 

But if good fortune in the circumstances of the time, 
or in the success of the enterprize, were to be arguments 
against the honours that history assigns, we should sink its 
greatest names to the level of the most obscure, and those 
who have changed the face of the earth, to those who pre- 
pared, by gradual steps, the means by which the changes 
were effected. In the history of a mechanical invention 
too, it may frequently appear, on a cursory examination, 
that those who by unsuccessful, although ingenious, efforts, 
actually retarded the progress of discovery, are as merito- 
rious as those, who convinced the world of the value and 
practical merit of their inventions. So soon, however, 
as success is attained, jealousy calls up all analagous pro- 
jects, however far from being adapted to the times at which 
they were proposed, or which some simple but undiscovered 
step prevented from being introduced into practice, and 
ranges them on an equal level with, or even exalts them 
beyond, those to whom the world owes the perfected inven- 
tion. 

Conflicting national pride too comes in aid of individual 
jealousy, and the writers of one nation often claim for their 
own vain and inefficient projectors, the honours due to the 
successful enterprize of a foreigner. 

If success be a title to honour in general history, it ought 
to be still more so in mechanical inventions. They require, 
to bring them into use, an union of practical and theoretic 
attainments, the want of either of which may render them 
abortive. Few projectors are thus doubly qualified, at the 
commencement of their career ; and few or none have been 
successful, until by long and costly experience, they have 
added practice to theoretic knowledge, or have by labo- 



HERO OF ALEXANDRIA 199 

rious study, brought science to the aid of mere mechanical 
skill. 

That steam is capable of exerting a mechanical force 
must have been obvious from the most remote antiquity, for 
we have no reason to believe that man was ever ignorant 
of the use of fire. But to apply steam to any useful pur- 
pose, is an idea comparatively recent. Still, however, the 
remotest antiquity that can be reached by profane history, 
has been quoted as affording an instance of the employ- 
ment of steam, if not for a useful purpose, at least for one 
that produced no unimportant effect at the time, and ex- 
cited the curiosity of mankind for centuries. 

129. The elder Hero of Alexandria, who lived about 
130 years before the Christian era, is the first author who 
gives any account of the application of the vapour of wa- 
ter. We are unable to quote his work in the original, but 
are indebted for a notice of it to the beautiful little treatise 
of Stuart, to which we, once for all, acknowledge our 
obligations.* In this work it is stated, that Hero expressly 
ascribes the sounds produced by the statue of Memnon, to 
steam generated in the pedestal, and issuing from its mouth. 
Now by the researches of Champollion, who is the highest 
authority on this point, the Memnon of the Greeks is iden- 
tified with Amenophis II., a prince of the 18th Egyptian 
dynasty, who reigned at Thebes 1600 years before Christ. 
Here then we have an application of steam, if the surmise 
of Hero be true, before the date of the Exodus of the Is- 
raelites. We must, however, express our opinion,'that this 
is rather an ingenious explanation of the philosopher him- 

* Historical and Descriptive Anecdotes of Steam-Engines^ and of their 
Inventors and Improvements^ by Robert Stuart, Civil Engineer. — Lon- 
don, 1829. 



200 



HERO OF ALEXANDRIA. 



self, of the mode in which he could have effected the same 
object, than an account of what was really performed by 
the Egyptian priests. 

130. Hero constructed or described more than one in- 
strument, entitled to the epithet of steam engine. Two of 
them, of which one would have answered to raise water, 
and the other, produced a rotary motion, are figured below. 





B 



In the figure marked b, a is a vessel in which water is 
boiled ; the pipe c proceeds nearly to its bottom ; the steam 
will therefore accumulate in the upper part of the vessel, 
and force the water in a jet through the pipe c. A foun- 
tain may thus be formed, on which may be supported the 
ball 0. 

In the figure marked c, o is a similar vessel ; two pipes, 
a and c, proceed from it ; these are bent towards each 
other, and serve as pivots to the sphere i, in which there 
are openings corresponding to those in the pipes a and c. 
From points in the sphere diametrically opposite to each 
other, proceed the pipes m and n, which are bent towards 
the end at right angles, and directed to opposite sides of 



HERO. 201 

the apparatus. The steam generated in the vessel o passes 
through the pipes a and c, into the sphere % and thence 
into the pipes m and n, issuing from which in opposite di- 
rections, it, by its reaction, gives a rotary motion to the 
sphere. 

Hero does n-ot give the slightest hint that his invention 
was capable of any useful application, nor does he appear 
to have imagined that he was in possession of an instrument 
that was in future ages to produce such important results* 

The Greek philosophers, however, seem rarely to have 
attended to the practical value of their investigations ; it 
was sufficient for them to discover and to astonish ; and 
even when they mention arts and instruments that seem to 
have been actually introduced, they avoid contemptuously 
all notice of their uses in the arts. " The ancient philoso- 
phers," says an ingenious author, "esteemed it an essential 
part of learning to conceal their knowledge from the unin- 
itiated ; and a consequence of their opinion that its dignity 
was lessened by its being shared with common minds, was 
their considering the introduction of mechanical subjects into 
the regions of philosophy, as a degradation of its noble pro- 
fession, insomuch that those very authors among them, who 
were the most eminent for their own inventions, and were 
willing by their own practice to manifest unto the world 
these artificial wonders, were notwithstanding so infected 
by this blind superstition, as not to leave any thing in wri- 
ting, concerning the grounds and matters of these opera- 
tions ; by which means it is that posterity hath unhappily 
lost, not only the benefit of these particular discoveries, but 
also the proficiency of these arts in general. For when 
once learned men did forbid the reducing them to vulgar 
use and vulgar experiment, others did thereupon refuse 
those studies as being but empty and Idle speculations ; 
and the divine Plato would rather choose to deprive 

26 



202 EOLIPYLE. 

mankind of those useful and excellent inventions than ex- 
pose the profession to the ignorant vulgar." We are 
luckily fallen upon happier times. The student and the 
proficient in science no longer shut themselves up from the 
busy world, or hide their acquisitions like mysteries from 
the public, but their whole endeavour is to bring their learn- 
ing into such a form as may calculate it for the most wide 
dissemination, and enable it to produce the most extensive 
usefulness. 

132. The Eolipyle, however, was an instrument well 
known to the ancients. It was applied by them to but one 
single object, that of exciting the energy of combustion. 
It is mentioned by Vitruvius, Lib. I. Cap. VI., as an illus- 
tration of the causes of the winds. It was supposed that 
the blast actually proceeded from the Eolipyle, but as steam 
would not support combustion, we must look to some other 
cause for its effects in this respect. We find it in the 
lateral communication of motion that takes place among 
fluids, by which a current of air is made to follow the course 
of the steam that issues from the neck of the Eolipyle. We 
give a figure of this instrument. 




CARDAN. 203 

It is composed of a globe or other hollow vessel A, to 
which a pipe B is adapted. If a portion of water be intro- 
duced, and the vessel placed over a fire, steam will be gene- 
rated and issue forcibly from the narrow apperture. If it 
be mounted on wheels it will recoil by the reaction of the 
escaping vapour ; and a rotary motion may be produced, 
by two pipes, but in opposite directions, as in the machine 
of Hero. 

133. A knowledge of some of the properties of steam 
seems to have been retained during the flourishing periods, 
and even to the decline, of the Roman empire. In the 
reign of Justinian, a dispute occurred between Anthemius, 
the Architect of that Emperor, and the Orator Zeno, which 
shows this fact. Yet the knowledge was here applied to 
mere purposes of private malice, while it might, by the 
exercise of no greater ingenuity, have produced important 
and useful consequences. From this period until the re- 
vival of learning, we find no record of any use of steam, 
either for useful or entertaining purposes. 

134. Cardan is the earliest modern author in whom we 
detect any hint of a knowledge of the mechanical proper- 
ties of steam. This extraordinary man, who united all the 
learning of his age with even more than all its superstition, 
appears to have known, not only the expansive force of 
steam, but the fact that a vacuum could be produced by 
its condensation ; a fact so important to the action of the 
steam engine. Among his proposals is one, for the use of 
the current of rarified air in a chimney, to produce a rotary 
motion. This, which is the original of the smoke-jack, 
we have seen exhibited recently in New-York, under 
the high sounding pretensions of its being a perpetual mo- 
tion. He, first of the moderns, gives a description of the 



204 



BAPTISTA PORTA. 



Eolipyle. The work which contains the former of these 
plans is dated 1571.* 

135. A German of the name of Mathesius, in 1571, to 
borrow the words of Stuart, "displayed almost as much 
ingenuity, in contriving to introduce so untoward a subject 
into a sermon as a description of an apparatus, answering 
to a steam engine, as would be required to invent the 
machine itself, and which he gives as an illustration, of what 
mighty efforts could be produced by the volcanic force of 
a little imprisoned vapour." 

136. The research of modern writers, among whom we 
may note with the highest praise, him that we have just 
mentioned, has disclosed various persons who seem to have 
had ideas more or less just of the mechanical power of 
steam. The only one that we consider worthy of notice 
is Baptista Porta, a Neapolitan, who lived towards the close 
of the sixteenth century. His machine, which is the germ 
of several that have been noted as original, is figured below. 




* Stuart's Historical Anecdotes of the Steam Engine, page 19. 



DE CAUSS BRANCAS. 



205 



Water is boiled in a vessel A, placed upon a furnace. 
The steam rises through the pipe b into the upper part of 
the box or vessel C, the lower part of which is filled with 
water. The pressure of the steam on the surface of the 
water, forces it up the rising pipe D. 



137. Next in the order of time is De Causs. 
various engines contrived by him is the following. 



Among 




A spherical vessel A has a pipe b b inserted, until it nearly 
reaches its lower part. The vessel is partly filled with 
water, which is boiled, and the steam accumulatmg in the 
upper part forces the water up the pipe. Here it will be 
observed, that the heated water is itself raised, and the 
powers and utility of the engine are evidently far less than 
those of the machine of Porta. 



138. The first person who seems to have had an idea, 
that the power of steam was capable of being applied to any 
other useful purpose, than that of raising water was Brancas, 



206 WORCESTER. 

an Italian, who proposed to direct the blast issuing from an 
Eolipyle upon the leaves of a wheel, which being set in 
motion by its impetus, might serve to move machinery. 
This method is unluckily imperfect and wasteful, yet the 
attempt is deserving the highest praise, inasmuch as he is 
the only person, who, in the infancy of these investigations, 
entertained any hope of realizing the vast benefits, that 
steam has since conferred upon the world. Had steam 
been confined in its action to the single object of raising 
water, it might have been of notable use in a few cases ; 
but its great and important value, as a prime-mover, has 
been only realized since methods of applying it, to any spe- 
cies of work whatsoever, have been discovered. 

139. This plan of Brancas was repeated by Bishop Wil- 
kins ; and Kircher proposed to apply two Eolipyles to 
concur in the same effect. The last named author also 
proposed an engine similar in principle to that of Porta. 

140. Of all those who attempted to apply steam to useful 
purposes, without being successful in introducing his engine 
into general practice, the Marquis of Worcester fills the 
greatest space. He has been claimed by English authors, 
as the first who made any experiments of importance upon 
steam ; and it has been asserted that the next of their coun- 
trymen, who undertook the investigation, did no more than 
copy without acknowledgement, the plans of Worcester. 
Even the first truly successful form the steam engine as- 
sumed, has been shown to be consistent, in many respects, 
with the description of one of the engines of this nobleman. 

It is yet a disputed point, what was actually the form of 
the engine of Worcester. His description is at best vague, 
and is without any figure ; various authors have exercised 
their ingenuity in framing plans of a machine that should 



WORCESTER. 207 

be consistent with the expressions of his work. We do 
not consider it important to do so, but shall content our- 
selves with quoting his own words. They are to be found 
in a little treatise, entitled .^^ tR century of the names and 
scantlings of such inventions^ as at present I can call to mintl 
to have tried and perfected, which, my former notes being losty 
I have at the instance of a powerful friend endeavoured, now in 
the year 1G55, to set down in such a way as may sufficiently 
instruct one to put the whole of them into practice.'''' This 
work was originally printed in London in 1663, and has 
since been six times reprinted ; the reprint of 1813, has 
been consulted for the following, being the 68th Propo- 
sition. 

" An admirable and most forcible way to drive up water 
by fire, not drawing or sucking it upwards, for that must 
be as the philosopher calleth it, infra spheram activitatis, 
which is but at such a distance, but this way hath no 
bounder, if the vessels be strong enough ; for I have taken 
a piece of a whole cannon, whereof the end was burst, and 
filled it three quarters full, stopping and screwing up the 
broken end, as also the touch-hole, and making a constant 
fire under it ; within twenty-four hours it burst, and made 
a great crack ; so that having found a way to make my 
vessels so that they are strengthened by the force within 
them, and the one to fill after the other, have seen the wa- 
ter to run like a constant fountain forty feet high ; one 
vessel of water, rarified by fire, driveth up forty of cold 
water ; and a man that attends the work is but to turn two 
cocks, that one vessel of water being consumed, another 
begins to force and refill with water, and so successively." 

Vague as this description is, it would still be possible to 
construct an engine that would perform a similar work 
by the expansive force of steam. It would be very inferior 
to modern engines, but would yet be effectual. 



208 WORCESTER. 

It has generally been imagined that this is the sole refe- 
rence to steam in the Century. But two others certainly 
correspond so closely to the character of our modern high 
pressure engines, that it may not be amiss to quote them 
also. They are the ninety-eighth and hundredth proposi- 
tions of his work. 

" An engine so contrived that working the primum mobile 
backward or forward, upward or downward, circularly or 
contrariwise, to and fro, upright or downright, yet the pre- 
tended operation continueth and advanceth, none of the 
motions above mentioned hindering, much less stopping 
the other ; but unanimously agreeing, they all augment 
and contribute strength to the intended work and opera- 
tion ; and therefore I call this a semi-omnipotent engine, and 
do intend that a model thereof be buried with me." 

** How to make one pound weight to raise an hundred 
as high as one pound falleth, and yet the hundred pound 
descending, doth what nothing less than one hundred 
pounds can effect. Upon so important a help as these two 
last mentioned inventions, a waterwork is, by many years 
experience and labour, so advantageously by me contrived, 
that a child's force bringeth up an hundred feet high, an 
incredible quantity of water, even two feet diameter, so 
naturally that the work will not be heard into the next 
room ; and with so great ease and geometrical symmetry, 
though it work day and night from one year's end to the 
other, it will not require forty shillings reparation to the 
whole engine, nor hinder one day's work ; and I may boldly 
call it the most stupenduous work in the whole world ; and 
not only with little charge to drain all sorts of mines, and 
furnish cities with water, though never so high seated, as 
well as to keep them sweet, running through several streets 
and so performing the work of scavengers, as well as furnish- 
ing the inhabitants with water enough for their private oc- 



WORCESTER. 209 

casions ; but likewise supplying rivers with sufficient water 
to maintain and make them portable from town to town, 
and for bettering of lands all the way it runs. With many 
more advantageous and yet greater effects of profits^ admi- 
ration, and consequence ; so that, deservedly, I deem this 
invention to crown my labours, to reward my expenses, 
and make my thoughts acquiesce in the way of further inven- 
tions." 

In the first of these, steam obviously meets the descrip- 
tion of his primum mobile, for in whatever direction it pro- 
ceeds it is still capable of exerting the same mechanical 
force. The single pound raising one hundred, in the 
second, meets the conditions under which the piston of a 
steam engine acts, for its weight bears even a less pro- 
portion to the power of the engine. 

The following is an extract from a manuscript left by 
the Marquis of Worcester. 

*' By this I can make a vessel of as great burthen as the 

river can bear to go against the stream. 

********* 

" And this engine is applicable to any vessel or boat 
whatsoever, without being therefore made on purpose ; 
and worketh these effects. It roweth, it draweth, it 
driveth, (if need be) to pass London Bridge, against the 
stream at low water." 

It is to be remarked, that Worcester claims, on his title 
page, the merit of having actually completed, and used all 
the inventions he describes in the work : in support of this 
assertion various evidence has recently been adduced. 

He employed a mechanic for thirty-five years, under his 
directions, in the manufacture of models ; and many of his 
projects that appear, in his manner of announcing them, 
absolutely impossible, have been unexpectedly realized by 
modern inventions. 

27 



210 WORCESTER HAUTEFEUILLE. 

That the steam engine of Worcester was no vague con- 
ception, but was actually put into operation, a recent dis- 
covery has settled, upon testimony the most convincing. 
The Grand Duke of Tuscany, Cosmo de Medicis, travelled 
in England, in 1656. His manuscript account of his jour- 
ney remained unpublished until 1818, when a translation 
was made and printed. The following is an extract from 
this translation : 

" His highness, that he might not lose the day uselessly, 
went again after dinner to the other side of the city, ex- 
tending his excursion as far as Vauxhall, beyond the pal- 
ace of the Archbishop of Canterbury, to see an hydraulic 
machine, invented by my Lord Somerset, Marquis of 
Worcester. It raises water more than forty geometrical 
feet by the power of one man only ; and in a very short 
space of time will draw up four vessels of water, through 
a tube or channel not more than a span in width." 

Here then, is a description of an engine in actual ope- 
ration, and corresponding in terms with that referred to in 
the century of inventions. 

141. In the several projects of which we have hitherto 
spoken, the expansive power of steam was used alone. It 
was made to act directly upon the surface of water to raise 
it ; or, issuing from the orifice of an Eolipyle, s.et a wheel in 
motion ; or again, issuing from two tubes attached to an 
Holipyle, caused that instrument to revolve upon an axis, by 
the reaction of the vapour. In each of these ways, the use 
of high steam is essential to success, and this upon a large 
scale is attended with danger, particularly in the lov/ state 
of mechanic arts, and before the various contrivances, we 
have mentioned in chapter III., were invented. 

The action of steam of a force no more than equal to the 
pressure of the atmosphere, against a vacuum formed by its 



MORLAND PAPIN. 211 

own condensation, is a far more safe, and as we have seen, 
more useful application of its energy. The researches of 
Stuart seem to show that this was first proposed by a French- 
man of the name of Hautefeuille. He, in the year 1678,* 
published a work in which he intimates that the alternate 
generation and condensation of the vapour of alcohol might 
be applied, without waste, to the production of mechanical 
effects. We have, however, no proof that this project ever 
went farther than the mere proposal. It is, notwithstand- 
ing, to be considered as one, far beyond the knowledge of 
that age, of the nature and properties of steam. 

142 Sir Samuel Morland, who was cotemporary, ap- 
pears, from the very words he employs, to have been 
merely an imitator of the Marquis of Worcester, and there- 
fore claims no notice among those who aided in the pro- 
gress of the steam-engine. 

143. In 1680, the year previous to that in which Sir 
S. Morland visited France, Dr. Denys Papin, a French 
Protestant, invented the safety valve, which has since been 
of such important service in the construction of the steam 
engine. It was first employed by him in an apparatus 
called the digester. This apparatus is a boiler, within 
which water is retained under pressure, in order that it 
may be heated, beyond the temperature at which it boils in 
the open air. The original object was to extract the gela- 
tinous matter from bones, in order to apply its solution as 
food. To prevent any risk of danger, a conical aperture 
was left in the lid of the vessel, and to this was adapted a 
conical stopper, pressed by a weight suspended at the end 
of a lever. It was in short, identical with the most usual 
form of safety valves at the present day. 

* Stuart's " Anecdotes." 



212 PAPIN — SAVARY. 

Although he thus employed water at a high temperature, 
and had discovered one of the methods that are still in use, 
of rendering the boiler safe, still,' it was long before he at- 
tempted to apply the power of steam. The motion of a 
piston in a cylinder, was suggested by him, as a method of 
adapting the^ expansive force of an elastic fluid to produce 
mechanical effects. In this apparatus, he at first proposed 
to employ air rarified by heat ; he next attempted ro ex- 
haust the space beneath the piston, and make use of the 
pressure of the atmosphere ; and finally, to raise the piston 
by the inflammation of gunpowder. In a letter to Count 
Linzendorf, however, he proposes to use steam for the same 
purposes. In the Leipzig Transactions, also, for the year 
1690, he repeats the proposition, and explains the princi- 
ple upon which he founds the application of this substance, 
both to raise a piston, and to'produce a vacuum by its con- 
densation. There is, however, no evidence that a separate 
boiler ever entered into his views, without which, it would 
have been impossible, to make any useful application of his 
principle. 

Nothing then, had been actually effected by Papin, in this 
earlier stage of his researches, and he did not extend them 
farther, until steam had actually been successfully employed 
in raising water ; if we can indeed say, that he ever was 
successful in pointing out a mode in which it could be ren- 
dered of practical value. 

144. The history of steam, applied to purposes of ac- 
knowledged utility, commences then with Savary. It has 
been much debated whether this person were in reality an 
inventor, or had merely the judgment to perceive an open- 
ing, for the introduction and adaption of previous discove- 
ries. His own statement is, however, clear, distinct, and 
worthy of credit. Having been, in the early part of his life. 



SAVARY. 213 

employed in the mines of Cornwall, he was aware of the 
vast expenditure incurred in keeping them free of water, 
and an accidental observation appeared to point out to him, 
a simple and easy mode, in which a substitute could be 
found for the expensive labour of animals. Being at a 
tavern in London, he threw upon the fire a Florence flask 
containing a small quantity of wine ; he observed the wine 
to boil, and a cloud of vapour to issue from the neck, while 
the interior remained transparent. Struck with the appear- 
ance, he seized the flask and inverted the neck in a basin 
of water; after a short time, he found the flask filled with 
liquid, in consequence of the condensation of the steam 
forming a vacuum, into which the water was raised by the 
pressure of the atmosphere. 

The very form and arrangement of his apparatus is a 
proof of the truth of his story, for it is no more than a flask- 
shaped vessel of iron in which a vacuum is formed by the 
condensation of steam. This part of its principle had not 
before been acted upon, nor even thought of, except in the 
suggestion of Hautefeuille, which we have before spoken of. 
The action of the vessel, is in this respect identical in prin- 
ciple with that of the common pump. He did not, how- 
ever, limit his views to this single action, but proceeded to 
add to it the action of the forcing-pump. For this purpose, 
so soon as the flask was filled with water, steam proceeding 
from the boiler, of a high temperature and corresponding 
tension, was admitted into the flask, after the communica- 
tion with the water beneath was closed, which acting on 
the surface of the water contained in the vessel, forced it 
up a lateral pipe. As it was impossible to obtain a perfect 
vacuum by the condensation of the steam, the first part of 
the action of Savary's engine was limited to the height of 
25 feet ; the second part has no limit, but in the tension of 
the steam, and the strength of the materials, of which the 



214 SAVARY. 

vessel and the rising-pipe were composed. This however, 
was, from the imperfect state of materials and workman- 
ship, limited to less than 70 feet, so that the two different 
actions of the engine, working in succession, raised the 
water to little more than 90 feet. Even at this compara- 
tively small limit, the danger attending the use of this en- 
gine became excessive, v/hile the height, to which it was 
capable of raising water, was entirely too small for the 
purpose of draining mines. Several different engines 
placed at different levels would have remedied the last 
defect, but the cost of attendance would been enhanced in 
proportion. Such defects were obvious ; there were, how- 
ever, others which could not be accounted for, until the 
doctrine of latent heat was discovered, and which we shall 
return to on a subsequent page. 

The cause that affects the action of high pressure en- 
gines, and prevents them from working with the power that 
might, at first sight, have been anticipated, is also to be 
found in operation in this engine. The force required to 
raise water, from sixty-five to seventy feet, is equivalent to 
steam of a tension of not less than three atmospheres ; now 
as the density of steam increases nearly as rapidly as its 
tension, it is obvious that to obtain this, in quantity sufficient 
to fill the vessel, would require the evaporation of nearly 
three times as much water as would fill it, were the tension 
no more than a single atmosphere. Hence, in fact, little 
is gained by the second part of the action of this engine ; 
for water may be raised, with an equal expenditure of fuel, 
nearly as high by condensations, in vessels placed at differ- 
ent levels, as it is by direct pressure of any intensity, 
however great. 

We have placed beneath a section of the engine of Sa- 
vary, which in its complete form was double, one vessel 
receiving the water in consequence of the condensation 



SAVARY. 



215 



of the steam, while from the other it was forced up by- 
direct pressure ; these vessels alternated with each other 
in their operation. 




I is the boiler in which the steam is generated. 

O, steam pipe, by which steam is conveyed to the vessel P. 

q q, pipe communicating with a reservoir beneath ; 
through this pipe the water is raised to the vessel P, where 
the steam is condensed, by the pressure of the atmosphere. 

S, rising-pipe through which water is forced when the 
steam flows from the boiler through a valve on the steam- 
pipe O, which is manoeuvred by the lever z m. 

R R, valves opening alternately. 



216 SAVARY. 

Xf reservoir to supply water of condensation ; it receives 
water from the rising-pipe S, through a pipe governed by 
a float and stop-cock. 

y, pipe through which the cold water falls on the outside 
of the vessel P. 

n, gauge-cock to show the height of water in the boiler. 

We have stated the more obvious defects of Savary's 
engine, as well as one which is not usually quoted. There 
is, however, another of far greater importance, but which 
rests upon a physical principle, entirely unknown at the 
period in which he lived. This grows out of the necessity 
of fining the vessel alternately, with steam of high tension, 
and water of a low temperature. 

When the steam is first admitted into the vessel, it will 
be condensed against its sides and upon the surface of the 
water ; nor will it begin to act mechanically, until both be 
heated to the temperature of 213°. Its full effect will not 
take place until both are heated to such a degree as will 
maintain the steam at a temperature, and consequent tension, 
appropriate to the height of the place of discharge. As the 
water is forced out of the vessel, fresh cold surfaces are ex- 
posed, and must be heated in their turn ; and when the vacu- 
um is to be formed, the outside of the vessel is cooled by the 
affusion of water, while the inside is farther cooled by the rise 
of water from the reservoir beneath. In these different ways, 
it has been found, by experiments carefully conducted, 
that y^ths of the steam is condensed without acting at all, 
and that of course, a similar proportion of fuel is wasted. 

The engine of Savary, therefore, is confined to a single 
object, namely, that of raising water ; and even this, for 
the reasons we have stated, it does to great disadvantage. 
Still, however, the introduction of this engine was not only 
important as a step to the construction of more perfect 
ones, but it was of itself of some value, when compared 



PAPIN. 



217 



with the methods for raising water that were at that period 
in use. 

145. An apparatus which, at first sight, bears a strong 
similarity to Savary's, was constructed by Papin, for the 
Elector of Hesse, in 1707. It differs in having a piston, 
working in the vessel into which the steam is alternately 
admitted and condensed, and makes no important use of 
the pressure of the atmosphere. It appears that, even with 
the aid of the celebrated Leibnitz, he had been unable to 
bring his cylinder engine to perfection, and had abandoned 
his researches, until again stimulated by the success of 
Savary. 

We give a figure of this last engine of Papin. 




a is the boiler, furnished with a safety valve 6, pressed 
down by a weight c, suspended from a lever. Water is in- 
troduced into the boiler through this valve. / is the forc- 
ing vessel, having an aperture at the top closed by the 
valve g. A piston is placed in this vessel, having a socket 
into which a cylinder of iron z^ heated red hot, is introdu- 
ced to keep up the temperature of the steam ; water is ad- 
mitted into the forcing vessel through the funnel x, and 
valve h. The rising pipe k enters an air vessel. The ac- 
tion of the steam in the forcing vessel, raises the water into 

28 



218 NEWCOMEN AND CAWLEY. 

he air vessel, whence, by the pressure of the condensed 
air, it runs in a continual stream ; when the piston has de- 
scended to the bottom of the vessel fy the valve d is closed, 
and no more steam flows over ; the valves c and g are 
opened ; through the former, the steam that has been used 
escapes, and through the latter the forcing vessel is again 
filled. 

146. The time had now arrived in which the world was 
to derive essential advantages from the employment of 
steam as a moving power. Even Savary's engine, although 
more valuable than any other we have hitherto spoken of, 
had obvious defects, which prevented its coming into gene- 
ral use. These obvious delects were remedied by the engine 
of Newcomen and Cawley, their patent for which issued 
in 1705. Departing from the idea entertained by all for- 
mer inventors, except in the abortive proposition of Papin, 
of making the steam act directly to raise water, either by 
acting upon its surface, or by forming a vacuum on its con- 
densation, Newcomen and Cawley sought the means of 
working the brake of a forcing pump. With this view, 
the pump-rod being loaded with a weight sufficient to bring 
it to rest in its lowest position, the brake or lever of the 
pump was made with equal arms, and resting on a pivot in 
the middle of its length. 

The pump-rod being thus loaded, and attached in this 
manner to one end of the beam, a piston, of size considera- 
bly larger than that of the pump, was attached to the other, 
and made to fit a Cylinder, at the upper end of which it 
rested, under the preponderating weight of the pump-rod 
and its load. The Cylinder had in its bottom a valve open- 
ing upwards, by which steam could be at pleasure admitted 
or cut off. To the side of the Cylinder and near its bot- 
tom was attached a horizontal pipe, bent upward, at the 



NEWCOMEN AND CAWLEY. 219 

open end ; in this was placed a valve opening to the air, and 
which is called the snifting valve. Steam of the tempera- 
ture of 212" being admitted into the Cylinder, would from 
its levity rise to the upper part of that vessel, displace the 
air previously contained therein, which flows out through 
the latter valve, making a sound which has given this valve 
its name. If the steam that thus enters the Cylinder, have 
its communication with the boiler closed, it may readily be 
condensed, and a partial vacuum formed, beneath the 
piston. The pressure of the atmosphere will now act, and 
force the piston downwards to the bottom of the Cylinder ; 
the opposite end of the lever-beam will be raised, and with 
it the pump-rod, and the weight with which it is loaded. If 
the communication with the boiler be again opened, the 
pressure on the opposite sides of the piston will again be- 
come equal, and the preponderating weight of the pump- 
rod will cause it to descend, and draw up the piston to its 
primitive position. A second condensation will cause the 
piston again to descend, and the process may thus be kept 
up, so long as the boiler continues to supply steam. 

The condensation in the Cylinder was at first produced 
by cooling the outside, by the affusion of cold water ; and, 
when the action was required to be rapid, by placing the 
cylinder in an external cylindrical space. A hole having 
been accidentally made near the bottom of the Cyhnder, 
the water spouted into it, and the condensation was found 
to be much more rapid. This was then imitated, by adapt- 
ing a pipe to the Cylinder, through which a jet was made to 
flow, as often as it was necessary to condense the steam. 
This pipe and injection apparatus, were governed by a stop 
cock or valve placed upon it. Thus there were two valves 
necessary to the action of this engine, and these were to 
act alternately, the one opening as the other closed, and 
vice versa. 



220 NEWCOMEN AND CAWLEY. 

147. In the original form of the engine, these were 
worked by hand, a boy being placed within reach of the 
levers that opened and shut them, to perform that opera- 
tion as often as necessary. This employment being ex- 
cessively irksome, one of the persons was not slow to per- 
ceive that it might be performed, even better than it could 
be by any personal attention, by the alternating motion of 
the lever beam itself. This important step towards the 
perfection of the engine, was made by a boy of the name 
of Potter, and was immediately adapted to all the engines of 
Newcomen and Cawley. 

It will be at once obvious, that the steam, in this engine, 
was employed solely to form a vacuum by its condensation, 
and that the pressure of the atmosphere was the efficient 
agent. Hence, as Savary's patent comprized the use of 
steam for this purpose, he was associated in the profits of 
Newcomen and Cawley. 

As this was the sole use that was made of the steam, it 
was unnecessary to generate it of a tension greater than 
that of the atmosphere ; hence its use became perfectly 
safe, while the height to which it was capable of raising 
water, was as great as could be effected by a forcing pump 
worked by any agent whatsoever. This engine, therefore, 
far exceeded that of Savary, both in its ease of application 
and its power. 

On the other hand, the principal physical defects, noted 
as affecting Savary's engine, were still inherent in Newco- 
men's, and its mechanical execution became far more diffi- 
cult. So great indeed was the latter difficulty, in the then 
imperfect state of the arts, that it was found impossible to 
keep the piston tight, except by covering its surface with a 
mass of water, whose presence still further enhanced the 
physical imperfections. The steam being condensed with- 
in the Cylinder, the whole was cooled down at each stroke 



NEWCOMEN AND CAWLEY. 221 

to the temperature of condensation, while the part of the 
Cylinder above the piston in its lowest position, was still fur- 
ther cooled, by the mass of water employed to render it 
tight. On the re-admission of the steam, the whole was 
again to be heated up to the boiling point ; thus the waste 
of fuel was quite as great as in the engine of Savary. 

Another imperfection grew out of the partial nature of 
the vacuum, that it was possible to produce in the cylinder. 
Water which boils under the ordinary mean pressure of the 
atmosphere at 212% rises into vapour at all temperatures 
whatsoever, and boils at lower temperatures under dimin- 
ished pressure. Hence, so soon as the piston began to de- 
scend, the action of atmospheric pressure was lessened by 
the generation of fresh steam, and although this was in its 
turn condensed, its place would be occupied by new steam 
of a lower temperature, and a resistance would be opposed 
to the descent of the piston. 

In consequence of this retarding force, it was found in 
practice, impossible to make the pressure of the atm.osphere, 
which is, at a mean, 151bs. per square inch-, act upon the 
piston with a mean force of more than T^lbs., and from 
this, in estimating the action of the machine, the friction, 
and other retarding forces^ are to be deducted. This en- 
gine, therefore, consumed about twelve times as much fuel 
as would have generated steam sufficient to fill the Cylinder, 
and worked with but half the force the moving agent was 
capable of exerting. 

The rectilineal motion of the pump and piston rods was, 
in this engine, accommodated to the circular motion of the 
ends of the lever-beam, in a very simple and ingenious man- 
ner. The ends of the beam were made in the form of arcs 
of circles, and the rods were suspended from them by 
chains, attached to the highest point of each arc. Thus as 
the active pressure of each of these, in the performance of 



222 NEWCOMEN AND CAWLEY. 

its share of the work was vertically downwards, it was 
always applied directly to the beam, the two rods being 
respectively, always in the direction oftangents to the cir- 
cular arcs formed upon the working beam. 

148. The valve apparatus of Potter, called by him the Scog- 
gan, was, in 1718, superseded by a more perfect arrange- 
ment invented by Beighton. A frame or bar was attached 
by a chain, working also over a circular arc, to the lever , 
beam ; projecting pieces or pins, forming a rack, were 
attached to the frame ; the valves were moved by quad- 
rants cut into teeth, and acting upon arack connected with 
the spindle of the valve ; to each of these quadrants was 
attached a lever, which was pressed by the pins upon the 
frame, through a circular arc, until it passed the line of 
motion of the frame, and was disengaged ; from this posi- 
tion, the lever was made instantly, to return to its original 
place, by the action of a weight. These levers being also 
furnished with handles, to enable the valves to be open and 
shut by hand, the apparatus was called the Hand Gear, the 
frame and pins, the Plug Frame. This mode of working 
the valves continued to be used up to the beginning of the 
present century, with but little improvement ; nor has it 
yet fallen wholly into disuse. 

The engine of Newcomen is exhibited in the annexed 
drawing, by which its mode of action and the uses of its 
several parts may be better understood. 



NEWCOMEN AND COWLEY. 



223 




a is the boiler. 

t, the steam pipe. 

c, the steam valve. 

c, the Cylinder, into v^^hich the injection water is seen 
playing through the valve and pipe p, 

r, the piston. 

5, the snifting valve. 

m, a reservoir of v^^ater, whence the injection pipe is sup- 
plied, and water flows through the pipe n to keep the pis- 
ton tight. 

The injection water is discharged through the pipe iy 
and the excess of that floating on the piston by the pipe h, 

w is the weight attached to the pump-rod, by the action 
' of which the piston is returned to its highest position. 



224 SMEATON — LEUPOLD. 

The lever beam and pump are too obvious to need de- 
scription. 

149. The engine of Newcomen and Cawley was improv- 
ed in its mechanical structure by Smeaton, and derived 
additional force from the general improvement of the me- 
chanic arts. Smeaton also formed tables of the dimensions 
of the several parts. With these improvements it is still 
occasionally used, particularly in places where fuel is 
cheap and abundant ; where its small cost, and its safety, 
are considered as more than counterbalancing the great 
waste of fuel with which it is attended. 

150. In 1718, a German engineer, of the name of Leu- 
pold, published a work containing a description of two en- 
gines, the merit of which he ascribes to Papin. They are, 
however, rather to be considered as ingenious applications 
of his own, of the principle of that inventor, aided by the 
knowledge of what had been effected by Savary and New- 
comen. In one of these, the steam was made to act alter- 
nately upon the surface of water in two vessels, and it is so 
similar in every thing, but the form and position of its parts, 
to the engine of Savary, that we do not conceive it neces- 
sary to describe it minutely. The second is a high pressure 
engine with pistons, and is extremely ingenious, besides 
being remarkable as the first in which steam of high ten- 
sion was made to act upon a piston. The first of these is 
liable to all the objections, that we stated in speaking of 
Savary's engine. The second is far better, and even pre- 
ferable in many respects to the engine of Newcomen. It 
is besides applicable to the production of a continuous ro- 
tary motion, and is therefore the first that could have been 
applied to general purposes in the arts. Of this last engine 
we have in consequence given a figure. 



LEUPOLD. 



225 




Steam is generated in the boiler c, and flows thence 
through the pipe d, it is represented as passing through one 
of the passages in a four-way cock, beneath the piston a, 
while the steam that had filled the other cylinder is escap- 
ing into the air through the passage e. The piston a works 
a lever and the pump-rod g, while h works another lever, 
and the pump-rod/. 

h is the fire-place. 

The two pumps force water alternately into the rising 
pipe i. 

Did the levers act upon cranks situated upon the same 
axis, a continuous rotary motion might be produced. 

Steam in this case is the moving power, and is not con- 
densed as in the engine of Savary. It, therefore, is con- 
stantly retarded by the pressure of an atmosphere, and 

29 



226 



LEUPOLD, 



must have a tension of at least two atmospheres in order 
to work to advantage. 

The history of the steam engine is thus brought down, 
from the most remote period at which the power of that 
agent was first suspected, until it assumed a definite form, 
and became capable of useful application. Hitherto, how- 
ever, but one species of work came directly within its 
scope. In the succeeding chapter, we shall find its phy- 
sical defects remedied or removed, and its application 
finally made universal, to every species of manufacturing 
industry. 



/ 



CHAPTER VIII. 

CONCLUSION OF THE HISTORY OF THE STEAM ENGINE. 

Power and Defects of Jfewcomeri's Engine. — Birth and edu- 
cation of Watt. — Professor Rohison. — Watfs first experi- 
ment. — Professor Anderson. — Watfs second experiment. — 
Inferences. — Separate Condenser. — Steam applied as the 
moving power. — Packing. — Jacket and Air-pump. — Work- 
ing Model. — Dr. Roebuck. — Experimental Engine. — • 
Wattes first patent. — Gainsborough's claim. — Boring ap- 
paratus. — Form of Wattes first Engine. — Saving of Fu- 
el, — Projects for rotary motion. — Fitzgerald, Stewart, and 
Clarke. — Double-acting Engine of Watt. — Washborough 
and Pickard. — Crank. — Sun and Planet Wheel. — Other 
Inventions and Improvements by Watt. — Hornblower, — 
Watt'' s patent extended. — Governor. — Introduction of steam 
into various mechanic arts. — Expiration of Watfs patent. — 
Cartwright and Sadler. — Murray, Maudslay, and Ful- 
ton. — Woolfe. — Oliver Evans. — Trevithick and Vivian. — 
Rotary Engines, — Conclusion. 

151. In the preceding chapter, the prominent defects of 
the engine of Newcomen and Cawley have been pointed 
out. In spite of these, it had been found of immense value 
in practice, in raising water for the supply of cities, and 
more particularly in draining mines. So great, indeed, had 
been the advantages derived from it in these cases, that 
hopes had been from time to time entertained that this en- 



228 WATT. 

gine might be rendered efficient in performing work of 
other descriptions ; and it had even been thought of as the 
means of propelling boats. That the energy of the prime 
mover was adequate to any of these purposes was certain, 
but mechanical difficulties opposed its application. Even 
had these been overcome, the engine was liable to physical 
imperfections, that had not at this period been suspected, 
far more formidable than those which are merely mechani- 
cal. The latter, we now know, are so great in amount, 
as to have prevented the atmospheric engine from compet- 
ing with almost any other prime mover, except in a few 
particular cases. These objections, whether physical or 
mechanical, might have been gradually removed ; the form- 
er by the general progress of the arts, the latter by the 
discoveries in physical sciences with which the close of 
the last century teemed. The steam engine, however, 
was not destined to wait for the slow changes, which follow 
the application of purely theoretic principles to practical 
purposes. A single individual was found, who, by his own 
researches and unaided efforts, reached the law of the re- 
lations of steam to heat, that was about the same time dis- 
covered in its more general form by Dr. Black. This illus- 
trious individual was James Watt. 

152. Watt was the son of respectable, but poor parents. 
His grandfather exercised the profession of a schoolmaster, 
his father that of a merchant in Greenock, in Scotland. 
Having received the elements of a liberal education, which 
the excellent school system of Scotland places within the 
reach of all. Watt, at the early age of sixteen, became the 
apprentice of a maker of optical instruments in the city of 
Glasgow. Two years afterwards he removed to London, 
and obtained employment from a maker of mathematical 
and philosophical instruments. In this employment, his 



ROBISON ANDERSON. 229 

health became affected, and he was compelled to return to 
his native district. 

In undertaking business on his own account, he would 
have preferred Glasgow, as offering far greater prospects 
of success than Greenock, and hence became anxious to 
settle in the former place. To this plan, however, obsta- 
cles presented themselves, in the form of the laws of the 
corporation, by which the exercise of a trade was restricted 
to those entitled to the privileges of a burgess, to which 
Watt had no claim. From this state of difficulty he was 
fortunately relieved, by the interposition of the professors 
of the University. This institution possessed, as a remnant 
of ancient privileges, the right of claiming immunity from 
the corporate restrictions, and Watt was furnished by them 
with apartments within the college buildings, in which he 
pursued his trade. 

153. His attention was first called to the subject of 
steam by Professor Robison, then a student of the Uni- 
versity of Glasgow, at a date as early as the year 1759, 
but their researches v/ere attended with no important 
advances. 

154. In 1761, Watt made experiments with an apparatus 
resembling the engine of Leupold ; but becoming aware 
of the danger attending the use of high steam on a large 
scale, he ceased from any farther pursuit in that direction. 

155. In 1764, he was employed by Professor Anderson, 
then holding the chair of mechanical philosophy in that 
institution, to repair a working model of Newcomen's 
engine. The obvious waste of steam that he found to 
attend the action of this model, and the great quantity of 
injection water it required, struck him as facts unaccounted 



230 WATT — BLACK. 

for by any previous scientific reason. Suspecting that the 
first defect might arise from an erroneous estimate of the 
comparative densities of steam and water, he, by a few 
simple experiments, endeavoured to ascertain the true 
relation, and found that water in becoming steam expands 
itself, under ordinary pressures, to 17 or 1800 times the 
bulk it had previously occupied. This is not far from the 
the truth, as we now know from more accurate experi- 
ments, and corresponded with the estimate of Smeaton. 
At this density for steam, his experiments shewed that six 
times as much steam, as was simply sufficient to fill the 
Cylinder, was expended at each stroke of the piston. He 
at once attributed this increased expenditure to the cooling 
of the Cylinder. The great quantity of injection water 
next engaged his attention, and the high heat the Cylinder 
retained, in spite of the large quantity admitted. By adapt- 
ing a bent tube, immersed in a vessel of water, to a com- 
mon tea-kettle, he introduced steam into the water, which 
was condensed and heated the water. By inquiring into 
the gain of weight that had taken place when the water 
reached the boiling point, he inferred that it required six 
times the weight of the steam, simply to effect it condensa- 
tion, without lowering its temperature, or that 1800 
measures of steam were capable of heating six measures 
of water to their own temperature, although derived from 
no more than one measure of water. Thus he reached 
experimentally one of the most important facts of the 
doctrine of latent heat, a doctrine that had been that very 
year taught in the same institution, for the first time, by 
Dr. Black. On communicating the result of his observa- 
tion to that distinguished chemist, he received from him an 
explanation of that doctrine, which furnished the con- 
firmation and rationale of the phenomenon he had ob- 
served. 



WATT. 231 

His experiments also shewed him that the pressure of 
steam increased in geometric progression, while its tempe- 
rature was raised in arithmetic. The decrease of tension 
at lower temperatures follows a similar law ; and hence, 
the pressure of the atmosphere on the piston never acted 
with a force greater than eight pounds per square inch. 

156. Thus, then, the cause of the imperfections of New- 
comen's engine, became apparent at one and the same 
time, by the aid of actual experiment, and by the applica- 
tion of the general theory of Black. But it was far less 
easy to point out the remedy for these defects, than to 
discover the cause. It was evident that to obtain all the 
power the steam was capable of exerting, the Cylinder 
should not be colder than the steam which entered it ; 
while on the other hand, the condensed steam, should not 
raise the injection water above the temperature of 100*, 
at the very outside, while a lower temperature would be 
preferable. The mode which he adopted, of meeting these 
two requisites, is as simple as it is ingenious ; yet it was not 
attained without great study and reflection on his part. 

157. It was not until a year after his performance of the 
experiments we have spoken of, that it occurred to him, 
that if a communication were opened between the Cylinder 
of the steam engine, and another vessel exhausted of air, 
the steam would rush suddenly into the empty vessel ; and 
that provided the latter were kept cool, by being immersed 
in water, or by injection, the steam would continue to fibw 
until the whole were condensed. 

158. With this idea he appears to have entertained, at 
the same time, the intention of using steam itself as the 
moving power, instead of atmospheric pressure, and his 



232 WATT. 

experiments on its elasticity had shewn him that a small 
increase in its temperature would probably give a very 
considerable addition of power. To effect the latter part 
of his plan, it would be necessary to make the pistourrod 
work air-tight, through a lid or cover adapted to the cylinder. 
A modification of the common air-pump had an arrange- 
ment that served as a model of the latter method, the 
barrel being covered by a lid, having at its centre a collar 
of leathers, by which the passage for the pump-rod was 
rendered air tight. 

159. It next became obvious that the piston could not 
be rendered tight in this case by keeping a mass of water 
floating upon its surface, for this liquid would have been 
speedily evaporated, and would have wasted much heat. 
Hence, more perfect workmanship would be required, and 

the packing must be moistened with a liquid that did not | 
boil, except at a temperature higher than that to which I 
the steam was ever raised. Oil is a liquid of this de- j| 
scription ; but tallow, which becomes fluid at a tempera- 
ture below that of ordinary steam, is still better. It is 
said that he originally proposed a packing of leather, but 
as this substance chars and cracks at a comparatively 
low temperature, it is unfit for the purpose, and bands of 
hemp were employed in its stead. 

160. To keep the cylinder from losing heat too rapidly, 
he conceived the idea of enclosing it in the Jacket. 

Two methods occurred to him, of keeping up a vacuum 
in the condenser. The first, was that of adapting to it a pipe 
thirty-four feet in length, and plunging at its lower end into 
areservoir of water ; the second, that of exhausting the ves- 
sel by a pump. The former being applicable in but few 
cases, he chose the latter for general use ; and we have, 
indeed, no instance of the first being applied in practice. 



WATT — ROEBUCK. 233 

161. These views were submitted to the test of experi- 
ment, first in an apparatus of small size, and finally in a 
working model, whose Cylinder was nine inches in diame- 
ter. The results were as satisfactory as his most sanguine 
expectations could have anticipated, and convinced him 
that he had discovered the means by which all the physical 
defects of the ancient engines could be remedied ; the steam 
no longer wasted by admission into a cyHnder cooled by 
injection ; and a vacuum far more perfect obtained, than had 
ever been before reached. 

The expense of constructing a steam engine, and the 
difficulty of inducing capitalists to embark in an untried 
scheme, seems to have deterred him from bringing it for- 
ward, and he devoted himself, for upwards of three years 
more, to pursuits far beneath the powers of his mind. 

162. It is even, at the present day, rare to find in men 
wholly devoted to business pursuits, that acquaintance with 
physical principles, which will enable them to judge of the 
merits of an improvement in the arts, that rests wholly on 
those principles. And such was the invention of Watt, 
which differed, as far as superficial examination could reach, 
from the engine of Newcomen, only in the addition of a 
cumbrous appendage, of which the light of physical science 
alone could exhibit the appropriate use, and manifest all 
the importance. For information of that description, it was 
in vain to seek among the traders of Glasgow at that early 
period, and Watt v/isely determined to keep his discovery 
to himself, until he could meet with a person qualified to 
appreciate its merits. Such a coadjutor he at last found 
in the celebrated D. Roebuck, a person to whom Great 
Britain is under great obligations as the founder of the 

30 



234 ROEBUCK — BOLTON. 

Carron works, in which the manufacture and application of 
cast iron was brought to that degree of perfection, which 
has added so much to the wealth of that country. 

Educated in the most liberal manner, and for a learned 
profession, he became an adept in all the chemical and 
physical sciences of the day, and had applied his knowledge 
to the establishment of a chemical manufacture whence he 
was deriving enormous profits. These he undertook to 
apply to mining for coal and iron at Kinneil, and to the 
establishment of the celebrated manufactory of iron, of 
which we have spoken. 

163. His scientific intelligence at once appreciated the 
whole merit of Watt's improvement, and he gladly furnish- 
ed the funds for constructing an experimental engine, which 
was tried in the drawing of water from one of the mines at 
Kinneil. This engine worked as well as had been antici- 
pated, and Watt was furnished by Roebuck with the means 
of securing his invention from piracy, in the form of a 
patent. 

In return for his advances. Roebuck became joint pro- 
prietor of the patent, and from his capital and influence, 
Watt had reason to hope for the speedy introduction of his 
invention into general use. But Roebuck had embarked 
in schemes beyond the reach of his finances, and of these, 
one, so far from being profitable, was ruinous to his fortune. 
The Carron works indeed flourished, but the mining specu- 
lation made no returns, and so far from being able to assist 
Watt any further, he was himself compelled to abandon, 
not only his least promising scheme, but also that which was 
going on successfully, and thus to leave to others to profit 
by the fruits of his intelligence and enterprize. In the 
wreck of his affairs, his share of Watts' patent passed into 
the hands of his friend Bolton of Birmingham. This skil- 



GAINSBOROUGH. 235 

ful and enterprising merchant, was not only well qualified 
to appreciate the merit of Watt's invention, but possessed 
the capital, by the aid of which alone, it could be brought 
into successful operation. 

164. The first patent of Watt is dated in March, 1769, 
and when an application was made to Parliament for its 
extension, opposition was made, on the plea that the most 
important part of his invention, the separate condenser, 
had been invented at a period, at least as early as the date 
of the patent, by a person of the name of Gainsborough. 
This claim was, however, set aside in consequence of clear 
and decided proof, that Watt's method was not only origi- 
nal with him, but earlier in date. 

165. It does not appear that any other of the methods 
by which Watt had rendered his engine so superior to 
all former ones, had occurred to Gainsborough or any 
other person. Still we have no reason to doubt, that 
Gainsborough had actually, and by investigations of his 
own, reached the plan of a separate condenser, and 
we cannot but believe, that the study of the doctrine of 
latent heat, might have led others, at a date not much later, 
to a similar discovery. That the improvements in physical 
science had rendered the world ripe for the introduction of 
Watt's invention, need be no diminution of his great merit ; 
for, if not the only one who thought of the remedies we 
have mentioned above, he was undoubtedly the first, and 
prior by several years to any other person. Nor is it 
merely by priority of invention that Watt is to be distin- 
guished ; there was a finish and completeness about every 
plan that emanated from his mind, which suited it at once 
for practical usefulness- 



236 WATT. 

This indeed was a peculiar trait of the genius of Watt ; 
invention was with him so much a habit, that he rarely 
examined any project without suggesting improvements, 
while caution, almost amounting to timidity, led him to keep 
back from the world his own discoveries, until he felt as- 
sured of their success. ^ This excess of caution would 
probably have retarded, if not wholly prevented his success, 
had he not been fortunate in his connexion with a partner, 
who possessed the boldest spirit of mercantile enterprize, 
united to the most consummate judgment and prudence. 
In this point of view, we may consider the world as being 
almost as much indebted to the intelligence and business 
ability of Bolton, as to the genius of Watt. 

English writers have spoken of Watt as ilhterate and de- 
ficient in education. If he is to be judged by the standard 
of classical knowledge, to which alone the name of learning 
is given in that country, the assertion might be true. But 
we should rather be inclined to cite him as an instance of an 
education exactly directed to the purpose of rendering him 
useful, in the important career to which he was called. The 
public schools of Scotland, if the mere pedantry of classical 
knowledge be neglected, give that species of instruction 
which extends the power of using the vernacular tongue 
for all business and practical purposes ; Watt besides be- 
came a good practical geometer, and his early pursuits 
compelled him to be acquainted with all the physical sci- 
ence that was then known. When to this was added 
practical skill in mechanical operations, we cannot but 
think that Watt had derived from education, that knowledge 
which was exactly suited to render him eminent. 

166. We have stated that the engine of Watt dispensed 
with the use of water, for the purpose of keeping the piston 



WATT. 237 

tight, and that a greater degree of accuracy was in conse- 
quence required in the workmanship. The Cylinders of 
steam engines are cast hollow, by means of a core that fills 
up a part of the mould. They are then reamed out and 
brought to the proper size by means of a borer, or tool affixed 
to a revolving axis. Great improvements in the boring of 
Cylinders were introduced by Smeaton at the Carron works, 
but the method was not, at the date of Watt's patent, so per- 
fect, as to give the interior a form wholly independent of the 
original shape of the cavity. But Watt had the advantage 
of receiving, just as he was about establishing a manufac- 
ture of steam engines at Bolton's works of Soho, near Bir- 
mingham, a new method of boring. This was the inven- 
tion of Mr. John Wilkinson, a proprietor of iron works, at 
Birsham, near Chester. Watt immediately availed him- 
self of this improvement, and was, by means of it, enabled 
to furnish Cylinders of a perfection of workmanship, that 
had previously been despaired of. In a Cylinder of fifty 
inches diameter, constructed by him at an early date, the 
greatest error was less than the sixteenth part of an inch. 
This perfection of workmanship was almost essential to the 
introduction of steam into general use, as a prime-mover of 
machinery ; for, although the process of raising water had 
been, and might still have been effected with advantage by 
Cylinders of less accuracy, the durability of the engine 
would, even in this very limited application of its powers, 
have been lessened, while the delicate operations it now 
performs, would have been impracticable. This method 
of boring was still further improved, until a six foot Cylin- 
der could be bored, with no error greater than the fortieth 
part of an inch. 



238 WATT. 

167. In the first engine of Watt, the piston was attached 
by chains to the lever beam, from the opposite end of 
which the pump-rod, loaded with a weight, hung. The 
primitive position of the instrument, is therefore, the same 
as in that of Newcomen, namely, the pump-rod preponde- 
rates and holds the piston in its highest attainable position. 
The engine has three valves, by one of which steam is admit- 
ted beneath the piston into the Cylinder, where it displaces 
the air and fills its cavity wholly. So soon as the Cylinder 
is thus filled with steam, this valve is shut, and the remaining 
two are opened ; through one of these the steam passes 
into the condenser, which acts to convert the steam into 
water, partly in consequence of the coldness of its sides 
kept constantly immersed in a. cistern of water, and partly 
by the aid of a jet of injection water ; through the other 
valve, steam flows from the boiler and presses down the 
piston, thus causing a motion at the opposite end of the 
beam, and raising the pump-rod. The piston having 
reached its lowest position, these two valves are closed. 
It thus becomes necessary, that the piston should be again 
raised to its original position, by the weight attached to the 
pump-rod. This might have been done, by allowing the 
steam situated above the piston to escape into the air, and 
permitting steam to flow into the lower part of the Cylin- 
der. The pressure on both sides of the piston being thus 
nearly equalized, the weight would have preponderated 
and raised the piston. But in this case a Cylinder full of 
steam would be condensed at each descent of the piston, 
and another allowed to escape, without effect, at each as- 
cent. The waste of the last mentioned quantity of steam 
was thus obviated by Watt ; a pipe was adapted to the 
side of the Cylinder, in which the two steam valves were 
placed, so that the communication, from the lower of these 
valves with the boiler, could only be eff*ected by opening the 



watt's single engine. 239 

upper one. Hence, in first filling the Cylinder, both of 
these valves must be opened at once, in all other cases 
they act alternately. The upper valve was placed above 
the passage by which steam enters into the upper end 
of the Cylinder, and thus only the lower steam valve inter- 
vened between the steam acting- on the piston from above, 
and that rushing into the condenser from below. The 
piston having reached its lowest position, the steam and 
condensing valves shut, and the valve in the side pipe 
opens ; a communication is thus made between the steam 
above the piston, and the part of the cylinder beneath it, 
the weight of the pump-rod then acting upon the piston, will 
meet with no other opposition than the friction of the piston 
itself, and the resistance which the steam experiences in 
passing through a pipe ; the weight will therefore prepon- 
derate, the piston will be drawn up, and the steam will 
circulate, from the upper side of the piston through the 
side pipe, and fill the space beneath the piston. 

The upper valve alone is a steam-valve, except when the 
engine is to be set in motion, when the second valve is 
opened with it, and admits steam to the lower part of the 
cylinder. In all other cases, the latter is merely a valve of 
communication, and may be called the equifibrium valve. 
The third valve may be called the condensing valve. 

This arrangement may be better understood by the 
inspection of the following figure. 



240 



WATT S SINGLE ENGINE. 




watt's single engine 241 

168. Still further to diminish the loss of heat, Watt 
pumped back the water of condensation into the boiler ; 
by these several improvements so great a saving of fuel 
was obtained, that the patentees asked no other remunera- 
tion for the use of the invention, except one-third part of 
the value of this saving. In a single mine in Cornwall, 
where three of their engines were employed, this compensa- 
tion was commuted for £8000 sterling per annum. 

The valves still continued to be opened and shut by an 
apparatus similar to the plug-frame and hand-gear of 
Beighton, but improved, and rendered more easy in its 
action ; the former became a part of the rod of the 
pump, by which the vacuum of the condenser was main- 
tained. The pump and piston-rods were still suspended 
by chains from circular arcs forming parts of the lever- 
beams, and the air pump rod was suspended in the same 
manner ; the latter therefore required a weight to return 
it downwards, after it had been raised by the beam. 

The condenser and pump underwent various modifica- 
tions before Watt was satisfied with their action, and finally 
assumed the form described in treating of the double- 
acting engine. 

169. Previous to the time of Watt, there had been but 
little demand for steam, as a moving power, for any other 
purpose than that of raising water, and for several years 
after his first researches, the state of the manufactures of 
England was not such as to require powers beyond what 
could be obtained from natural waterfalls, or the action of 
the wind. Savary had indeed proposed to make the water 
raised by his apparatus fall upon an over-shot wheel, and 
thus to apply the power of steam to any manufacturing 
purpose whatever. Similar projects had been entertained 
in relation to the Engine of Newcomen. Neither of these, 

81 



242 STEWART — CLARKE. 

however, could have been applied to any advantage, in 
consequence of the great cost of fuel they must have occa- 
sioned, particularly as the effective power of a wheel is 
considerably less than the absolute mechanical force of the 
water employed. 

The several projects of steam-boats that we shall here- 
after speak of, necessarily required rotary motions, but 
these were all imperfect and abortive. Leupold's engine 
alone, had the two pistons been applied to cranks situated 
upon the same axis, could have produced a rotary motion ; 
but the inventor does not appear to have been aware of the 
value of this part of his own invention, or at least did not 
consider this application of it of importance. 

170. In 1757, a person of the name of Fitzgerald at- 
tempted to take off a rotary motion from the piston of 
Newcomen's engine by means of ratchet-wheels, that 
could be forced forwards during the descent of the piston, 
but would remain fixed during its ascent. The continuity 
of the motion was to be kept up by a fly-wheel. This was 
too imperfect a method to be successful, and had no result. 
A similar project was entertained by persons of the names 
of Stewart and Clarke, who attempted to apply it to sugar 
mills in Jamaica, but this like the other, was abandoned as 
impracticable, or useless. Still later, at a colliery in Eng- 
land, a drum for raising coal had been worked by an 
atmospheric engine, but even this rude apparatus was but 
imperfectly driven. Hence it was left for Watt to fit the 
steam engine for general use, as well to improve it in its 
application to the sole purpose, in which its energies had 
been successful, before his day. 

171. The first step towards making the steam engine 
capable of producing a continous motion in machinery. 



watt's double engine. 243 

was to make the piston work during its ascent as well as its 
descent, for both in the atmospheric engine, and the first 
engine of Watt, the moving power is exerted only to press 
down the piston, and it is afterwards returned to its origi- 
nal position, by the action of a counterpoise. 

Watt, whose caution was equal to his genius, proceeded 
in his inventions by slow and gradual steps. His first 
engine hardly varied from Newcomen's in external form, 
and was in truth, rather a great and all-important improve- 
ment upon that imperfect apparatus, than an invention 
absolutely original. In the same manner his double-acting 
engine was obtained by a slight and simple alteration of his 
former one. It was required that the piston should be 
forced upwards as well as downwards by the steam, he 
effected this by adding one additional valve to the three 
employed in his single-acting engine. The equilibrium 
valve of the single engine became a steam valve, instead 
of serving as a mere communication between the opposite 
sides of the piston, and the valve that was added was one 
forming a communication between the condenser and the 
upper part of the cylinder. Hence it was necessary that 
the steam-pipe should extend to the lower pair of valves, 
and the condensing pipe to the upper ; the side pipe was 
thus doubled. The improved hand gear of Beighton was 
still retained, to open and shut the valves. 

The mode of operation of this engine has already been 
fully explained, it is therefore unnecessary to repeat it 
here. But it did not at first assume the perfect form in 
which it has been represented in chapter IV. The steps 
by which Watt proceeded were as follows. The rectiline- 
al motion of the piston-rod having been rendered capable 
of exerting an equal force, both during its ascent and 
descent, a connexion with the beams by chains was no 
longer sufficient ; for although they would be efficient in 



244 WASHBOROUGH — PICKARD. 

drawing the beam downwards, their flexibility would not 
admit of their forcing it upwards. It hence became ne- 
cessary that their connexion should be made of a rigid 
material, and yet in such a manner as to permit the recti- 
lineal motion of the one, to accommodate itself to the 
circular motion of the other. True to his general system 
of slow and cautious improvement. Watt attempted at first 
no violent alteration. The circular end of the lever beam 
was merely cut into teeth, or rather had a toothed segment 
bolted to it, and for the chain a rack was substituted, 
which caught into the teeth of the segment. Thus the 
stroke of the piston became effective, both during its ascent 
and descent. It will be obvious, however, that this is a 
rude and imperfect method, and he speedily contrived a 
better in the shape of the parallel motion. 

172. About the time that Watt undertook to adapt his 
principle to general purposes, an engineer of the name of 
Washborough attempted to attain a similar end, by means of 
the atmospheric engine. His plan was very similar to Fitz- 
gerald's, and was improved by Pickard. Engines of their 
joint construction came into use in Gloucestershire, and 
at the block manufactory of Mr. Taylor, at Southampton. 
The first actual application of the crank to the steam 
engine, seems to have been due to Pickard. 

173. Watt however at an earlier date, conceived the idea 
of making two single-acting cylinders act upon cranks situ- 
ated upon the same axis, and thus produce a continuous 
rotary motion. In the attention, which the introduction of 
his engine into use for raising water required, this idea 
was suffered to remain unimproved until he had completed 
the plan of making the engine double-acting, and of com- 
municating the motion of its piston to the beam, by the 



CRANK. 245 

rack and toothed segment. To apply the motion thus 
obtained to general purposes, it became necessary, to con- 
vert the reciprocating motion of the beam into one contin- 
uous and rotary. That a crank was the most simple and 
obvious means of performing this has already been shown, 
and Watt recurred at once to the idea we have stated 
above, as having suggested itself to him, except that in the 
double-acting engine but one crank would be necessary. 
Various simple and familiar instruments have rotary mo- 
tions, that are produced by this instrument. Among these 
may be mentioned, as of most frequent occurrence, the 
Potter's wheel ; the turning lathe ; and a variety of the 
spinning wheel, then in constant use, although now nearly 
obsolete* The friends of Watt assert that his views were 
communicated by a workman, who passed from his em- 
ploy to that of Pickard, but there is no reason why both 
may have not fallen upon the same simple and obvious plan 
of producing the same kind of motion. Be this as it 
may, Pickard took out a patent for the application of the 
crank to produce a rotary motion in the Steam Engine, 
and Watt satisfied that his own ingenuity could provide a 
substitute, did not attempt to contest it, but left it as an 
obstacle in the way of his other competitors. 

174. To produce the effect that the crank was intended 
to perform, he adapted to his engines an apparatus called by 
him the sun-planet wheel. This is represented on the 
following page. 



246 



SUN-PLAIVET WHEEL. 




jr. Connecting Rod. 

z Zy Flj-wheel. 

a, Wheel fixed upon the axis of the the fly-wheel. 

h. Wheel revolving upon a pivot at the extremity of the 
connecting-rod. 

The wheels a and 6, having equal radii, whose sum is 
equal to the length of the stroke of the engine, the teeth of 
the wheel h will apply themselves to those of the wheel a, 
during the whole motion of the engine. The wheel h will 
turn the wheel a around, and cause the axis of the wheel, 
to which the latter is attached, to revolve. The former 
wheel will also itself revolve. 

It will be obvious that the axis of the fixed wheel must 
revolve twice as fast when driven in this manner as it does 



WATT. 247 

when propelled by means of a crank ; there are, in conse- 
quence, cases where it may be better suited to the required 
work than the crank ; such was the case in the earlier adap- 
tations of Watt's engine to manufacturing purposes. When 
however, in his subsequent engines, a crank furnished a 
better and more suitable speed, he did not hesitate to 
employ it, confident in the priority of his own claim to its 
application. 

175. We have thus seen Watt taking up the engine 
in a very imperfect state, gradually perfecting it in its 
application to its ancient purpose, and finally rendering it 
universal in its uses. He also made many accessory im- 
provements, by which its use was rendered more easy and 
certain. Of these we may particularize the steam-guage, 
the barmometer guage for the vacuum of the condenser, 
the self-acting feeding apparatus, the self-regulating damp- 
er, and the form of boiler which is yet most generally 
employed with double-acting condensing engines. 

Under his directions the hand-gear of Beighton was 
first improved, and finally superseded by the eccentric, and 
the long slide valve was introduced. The eccentric and 
slide valve were claimed also by Murray of Leeds, but 
although he may, perhaps, be entitled to the merits of a 
separate discovery, Watt was successful in showing the 
priority of his own claim to them. 

After the parallel motion was added to the engine, the 
beam still continued to be of wood, as was the connecting 
rod. Subsequent steps led to the substitution of the more 
inflexible material cast-iron, and the pivots of the parallel 
motion, instead of being, as before, placed beneath the 
beam, were now cast upon it, and turned down to the 
proper size and shape. Frames and pillars of iron to 
support the beam were gradually substituted, for the floors 



248 HORNBLOWER. 

of buildings, and walls, that were at first used ; brass boxes 
forming the sockets for all the circular motions were 
introduced ; and the external beauty of the machinery 
improved by perfection of finish, that added equally to the 
power and durability of the engine. It was in 1778, that 
Watt made the piston act during both its motions, and he 
did not cease, to the very end of his life, to extend its use- 
fulness, and improve its structure. 

No valuable addition to the condensing engine was made 
except by himself or under his direction, if we leave out 
those of Murray, which we have mentioned, and to which 
Watt was able to substantiate an earlier and more authen- 
tic claim. 

176. The application of steam acting expansively is also 
due to Watt. One of his single engines employed it in 
this manner at Soho, as early as 1776 ; and he used it also 
in his double-acting engines almost from their first con- 
struction. We have seen, in another place, that he did 
not reap all the advantages of which this method is capable, 
nor was he permitted to hold it, as an invention of his own, 
without contest. Two brothers of the name of Hornblower, 
in 1782, took out a patent for the use of the same principle, 
but by means of two Cylinders. In the first of these the 
steam acts by its tension, and produces an effect equal to 
that which it does in the high pressure engine. On escap- 
ing from this it enters a second and larger Cylinder, in 
which it expands, and from the opposite side of whose 
piston the steam flows alternately to the condenser. Thus 
then, the resistance, which the atmosphere opposes to high 
steam, is removed, and the eff*ect of its expansion brought 
into play. As the separate condenser interfered with the 
patent right of Watt, this plan could not be brought into 
use, nor was it desirable that it should, for an engine of 



CONICAL PENDULUM. 249 

equal power on this construction is more costly than that 
of Watt, and it is difficult to make the two Cylinders 
employed, one containing high, the other expansive steam, 
act in such harmony, that one of them shall not be retarded 
by the other. 

177. Five years ot Watt's patent had run out, before he 
had fairly introduced his single engine into use. He 
therefore made application, in 1775, for an extension of the 
usual period, and the application was, after much opposi- 
tion granted. Thus by a noble effort of national gene- 
rosity the profits of his discovery were secured to him for a 
term of years sufficient to remunerate him for his labours 
and sacrifices. The patent-right thus extended became 
the object of a series of attacks, leading to judicial investi- 
gation ; but in spite of the interested and continual oppo-" 
sition, the patent was in every case maintained. 

It is, indeed, highly to the credit of the institutions of 
Great Britain that this long contest, should, in all its points, 
have been constantly decided in favour of him to whom 
the world, after an interval that has deadened all partial 
feeling, assigns unanimously the merit of discovery. Such 
an honourable result, we fear, could hardly have been at- 
tained in our own country, in which the most carefully 
guarded patent-rights are proverbially insecure, and those 
inventions which have added most to the national wealth, 
have been those that have been of least pecuniary value to 
the inventors. 

A conical pendulum had been applied to mills of various 
descriptions before the time of Watt. The suggestion of 
the valuable use, to which it might be'applied in the steam 
engine, is said to be due to a Mr. Clarke, of Manchester ; 
we do not, however, know whether he ever applied it in 
practice. It was, whether as an original invention of his 

32 



250 watt's double engine. 

own or not, speedily adopted by Watt, and adapted to all his 
engines where regularity of motion is needed. 

178. The patent for Watt's double-acting engine is 
dated in 1782, and in the same year one was erected at the 
Bradley Iron Works on this principle. It had the toothed 
segment on the lever beam, and a rack attached to the 
piston-rod. Since that period, the improved engine has 
been introduced to a very great extent in the manufacture 
of iron ; for impelling the blowing apparatus in blast fur- 
naces, and for rolhng, hammering, and slitting wrought 
iron. 

The patent for the parallel motion was issued in 1784, 
and in that year the Albion Flour Mills were erected in 
London. 

Two of Watt's double-acting engines, of 50 horse power 
each, were applied to drive twenty run of mill stones ; the 
establishment was conducted with great profit until the 
year 1791, when the building, with all the machinery and 
stock, was consumed by fire. It was suspected, at the 
time, to be the work of an incendiary, instigated by those, 
who, by the aid of other prime movers, were unable to 
compete with the improved agency of steam. The experi- 
ment, however, was so far successful, as to satisfy all, that 
the engine might be advantageously adapted to almost 
every species of manufacturing industry. 

In 1785, the first cotton mill moved by steam was 
erected by Messrs. Robinson and Papplewick, in Notting- 
hamshire. In 1788, a coining apparatus for copper was 
erected at Soho, and driven by a steam engine ; the ma- 
chinery 'there applied has been imitated at the Royal Mint 
of Great Britain and the Imperial Mint at St. Petersburgh, 
and all were set in motion by double-acting engines on 
Watt's construction. 



CARTWRIGHT SADLER. 251 

In 1793, cotton was first spun at Glasgow by steam. 
In the year 1793, it was introduced into the woollen, 
worsted, and flax manufactures, and in 1797, was employed 
at Sheffield for grinding cutlery. 

179. In the year 1800, the extended term of Watt's 
patent expired. Up to this time, the introduction of his 
engine into use had been slow. This has been ascribed 
to the prejudice entertained against the monopoly, but 
probably is in some measure due to the fact that the arts 
did not keep up with the rapid improvement of the steam 
engine. At this date the steam engines, in London, did 
not exceed 650 horse powers ; in Manchester, 450 were 
in use, and about 300 at Leeds ; while upon our own con- 
tinent but four engines of any importance were to be 
found, two of them at Philadelphia and one at New-York, 
all employed for raising water. 

180. During the continuance of Watt's patent, various 
plans were proposed, which were rendered abortive, in con- 
sequence of his being in possession of the sole right of 
using the only plan by which low pressure engines could 
be rendered efficient, the separate condenser. Hence, 
with the exception of Hornblower, against whom Watt 
and Bolton obtained a verdict, there are no important 
names to be mentioned, except those of Cartwright and 
Sadler ; these two engines are chiefly remarkable for the 
suppression of the lever beam. 

Watt, as we have already stated, proceeded, in his im- 
provements, slowly and gradually, and they were all 
applied to the form in which he found the engine existing. 
Hence the beam, a heavy and cumbrous appendage, formed 
a constant part of all his engines, as it had done of the 
original pumping engine of Newcomen. The parallel 



252 CARTWRIGHT — SADLER. 

motion, the connecting rod, the sun and planet wheel, 
the rods of his air, cold, and hot water pumps, were all 
adapted to this part of the ancient apparatus, and from the 
use made of it in working the latter, it appeared to be 
almost indispensable. In Cartwright's engine the beam 
was suppressed altogether, and with it the separate pumps. 
A cross-head was placed upon the piston rod, bearing two 
short connecting rods, that turned the cranks of two 
wheels of equal diameter catching into each other, and a 
pinion attached to the axis of the crank was driven by one 
of them. As this engine did not work as well as the 
double-acting engine of Watt, it merits no further notice, 
at this stage of the history ; although had it appeared be- 
fore the improvements of Watt, it would have been of 
great value. Cartwright is, however, to be mentioned with 
high praise, as the inventor of the metallic packing for pis- 
tons, which, as has been stated on a former page, promises 
to supersede all others. 

Sadler's engine was a single-acting engine, differing from 
Watt's principally in the position of the equilibrium valve, 
which was situated in the piston itself. A wheel was fixed 
to an axis passing, at right angles, through the top of the 
piston-rod ; this worked between guides, and on the oppo- 
site end of the axis was placed the connecting-rod that 
turned the crank of the fly-wheel. The rod of the air- 
pump was worked by a short lever, the centre of whose 
motion was at the end, instead of the middle, as in the an- 
cient beam, and which, having no other work to do but 
that of pumping, was much lighter than the latter. 

From the date of the expiration of Watt's patent, the 
use of the double-acting condensing engine has been 
extended in a rapidly increasing ratio, insomuch that far 
more engines are now made at Soho, in spite of the ardent 
competition of various other manufacturers, than were 



I 



MURRAY — WOOLFE. 253 

ordered while Watt was possessed of the sole right of 
making engines as well as using his principle. 

181. The improvements made in the condensing engine 
since that period, have principally consisted in the finish 
and perfection of the parts, and in this Murray of Leeds 
has been most distinguished. His engines having a beauty 
of proportion, and accuracy of workmanship, exceeding 
most others. In England, the beam has been continued 
in almost all cases except in the engine of Maudslay, while 
in this country it has, in many instances, been laid aside. 
The first engines constructed in America for Fulton's steam- 
boats have the form represented in PI. VII. which is superior 
to that of either Sadler or Maudslay. Where the beam is 
retained, the parallel motion has been superseded in several 
American engines, by a simple slide to guide the connecting 
strap. The adaptation of this to the lever beam is the 
invention of Mr. R. L. Stevens, whose name we shall have 
occasion to quote hereafter as a successful constructor of 
steam-boats. 

The eccentric and slide valve belong to this last period 
of the history of the double-acting engine, but their inven- 
tion has been already referred to. 

182. The use of the expansion of steam has been stated 
to have originated with Watt, and we have mentioned the 
attempt of Hornblower, to adapt the same principle to an 
engine composed of two Cylinders. This, which was 
defeated in consequence of its interfering with Watt's 
patent, was revived in 1804 by Woolfe, with a boiler for 
generating high steam. This engine has been found to 
work to great advantage ; but for reasons mentioned in 
speaking of Hornblower's engine, it will be obvious that 
steam of equal tension would act to greater advantage in 



254 EVANS. 

an engine composed of but a single Cylinder. This last 
method has received great extension in several American 
engines, but is yet far from having attained the perfection 
in practice, of which a consideration of its theory has 
induced us to consider it susceptible. 

It has been seen that the plans proposed during the term 
of Watt's patent, v^ere either such direct infringements as 
to be prohibited by legal proceedings, or wholly inferior in 
utility to his inventions. The very year, however, that saw 
his patent expire, also saw the introduction into use, of two 
engines, that, had they been brought to perfection before, 
might have competed with that of Watt upon equal terms. 
For the history of one of these, we are compelled to go 
back almost to the date of Watt's earlier discoveries. 

183. Oliver Evans, well known in this country as an 
excellent mill-wright, entertained the idea of the possibility 
of propelling wagons by the action of high steam, as early 
as 1772. Soon after, he ascertained, by experiment upon 
a small scale, the practicability of so doing ; and in 1786, 
applied to the State of Pennsylvania, which (under the old 
Confederation) had not parted with this attribute of sove- 
reignty, for an- exclusive privilege. It is well to remark 
that his engine was intended to be double-acting, and that 
even this last date is but little later than the construction of 
the engines for the Albion mills, whose principle was long 
kept secret by Watt. His applications, both for private 
and public patronage, were treated as the reveries of in- 
sanity, and it was not until 1801, that success in his pro- 
fession enabled him to raise the funds for erecting an 
experimental engine. This was first applied to grind gyp- 
sum, and afterwards used in sawing marble. It was pub- 
licly exhibited in Philadelphia in that year. 

In 1804, he was employed by the corporation of Phila- 



TREVITHICK. 255 

delphia to construct a dredging machine worked by steam, 
with which he made successful experiments, both on loco- 
motion, and navigation by steam, that will be mentioned 
in their proper place. Not the least of the improvements 
of Evans lies in the form of his boilers, which he was the 
first to make in the form of a cylinder ; a form that we 
have already shewn to be preferable to any other yet pro- 
posed. His first experiments were made with a gun bar- 
rel, and he steadily adhered to that form in his subsequent 
operations. 

The engine of Evans retained the lever beam of Newco- 
men, and has been copied in this respect in many Ameri- 
can engines, of which the beautiful one figured on PL V., 
is a specimen. In others, the arrangement in PI. VII. has 
been adopted, and others again are horizontal, as repre- 
sented on PI. VI. The latter form has hitherto been 
principally used on the Mississippi and its branches. The 
high pressure engine came more early into general use in 
the United States, than it did in Europe, and long experience 
has rendered its proportions better understood in our coun- 
try, than they are in England. It is with us the favourite 
form, except in the steam-boats of the Atlantic coast. In 
these, a fear of the greater danger, with which it was thought 
to be attended has prevented, its introduction. It seems, 
however, to be now almost conceded, that, with proper 
precautions, boilers generating high steam may be render- 
ed as safe as any others, and hence the conclusion has been 
drawn that high steam, acting expansively, as it is the most 
powerful application of steam, will, wherever circum- 
stances will admit, supersede all other methods. 

184. The year 1801 also witnessed the construction of 
the high pressure engine of Trevithick and Vivian. The 
boiler in this case was a Cylinder of cast iron ; the fire was 



256 ROTARY ENGINES. 

made within it, and hence it is less safe than the boiler of 
Evans. The Cylinder was immersed in the boiler, in order 
to retain the heat of the steam. In the first engines it was 
attempted to condense the steam ; but this is always at-. 
tended with disadvantage, unless when the steam has had 
an opportunity of cooling itself by expansion. The fly- 
wheel, connecting rod, and crank were above the Cylinder, 
and no parallel motion or beam was needed. In the ap- 
plication of the engine to locomotion, a plan of connecting 
rods like those on PL VII. was finally adopted, but, so far 
as we can learn, only one connecting rod was used at first, 
even in this case, as in the engines of Sadler and Maudslay. 
Such is the history of the engines that are now in actual 
use, or have served as steps to the present state of the art. 
Another class remains to be mentioned. 

185. Watt had included in his first patent a method of 
producing a rotary motion by the direct action of steam, 
but had with sound judgment abandoned it, in favour of 
a double-acting Cylinder engine. In spite of this virtual 
acknowledgment of the inferiority of this principle, innu- 
merable projects have since been entertained of rotary 
engines. The result of these experiments may be sum- 
med up in a few words. The advantage to be derived is 
in fact of but little moment, while the mechanical difficul- 
ties that lie in the way are such as have hitherto prevented 
any experiment on rotary motion, produced by the direct 
action of steam, from being successful. 

The Cylinders of engines have occasionally been sus- 
pended on trunnions ; in this case the piston-rod may be 
applied directly to the crank. The earliest of these was 
one constructed by French in 1808, in a steam-boat in the 
Harbour of New-York, a model of which of the same 
date is among the apparatus of Columbia College. 



WATT. 257 

186, In the brief sketch we have thus given of the 
History of the Steam Engine, many ingenious contri- 
vances and inventions have been passed over. These 
have been omitted for want of space, and because few of 
them, however ingenious, have had any prominent effect 
in introducing the steam engine into more general use. 
The different forms of boilers that have been proposed, or 
even actually used, would occupy no small room. The 
object of our essay is, however, accomplished when the 
engine has been traced, from its first rude beginning, to 
those forms in which it is found in most common use, and 
when we have noticed those different inventions, that have 
tended to faciliate its progress, or by which it has been 
fitted the better to subserve the purposes for which it was 
invented. The most important step is undoubtedly that 
made by Watt, and it is remarkable in the history of the 
arts, not more for the immense value that it has had in its 
practical application, than for being the result of scien- 
tific research, and the study of physical principles, by the 
most elegant and accurate processes of induction. 



33 



CHAPTER IX. 

APPLICATIONS OP THE STEAM ENGINE. 

General view of the applications of the Steam Engine. — 
Raising water. — Grinding corn. — Cotton Spinning. — 
Jfavigation. — Bossufs laws of the impact of fluids. — 
Principles of the action of Paddles. — Juan^s laws of the 
action of fluids on solids moving in them. — Maximum 
speed of vessels. — Power required to propel paddles. — 
Relation between the power and the surface of the Paddles. — 
Laws of the motion of Steam-boats. — Theory of paddle 
wheels. — Comparison between theory and observation. — 
Practical Rules. — Steam-boat engines. — History of Steam 
navigation. — Application of Steam to Locomotion. — His- 
tory of the Steam carriage. — Conclusion. 

187. The steam engine is now applied to almost every 
species of manufacturing industry, and as a substitute for 
the labour of men and animals in almost every art, and in 
many of the other cases in w^hich they were formerly 
employed. In its earliest forms it was used to raise water, 
and still in its more perfect shapes fulfils the same object ; 
it performs almost every variety of manufacturing mani- 
pulation ; propels vessels through the water ; and drags 
carriages upon railways, and even upon common roads. 

188. In raising water, pumps may be adapted to the 
beam of the engine, and the useful effect may be safely 
taken, at the raising of 240001bs. one foot high, for every 



260 STEAM-BOATS. 

horse power of the engine, estimated in the manner that 
has been pointed out. 

189. In Grist mills, it is estimated that the power of 
five horses is necessary for every run of stones, and for 
performing the work necessary to supply them, moving the 
whole of the usual labour saving machinery. In applying 
the engine to this purpose, rotary motions of the proper 
velocity are taken off from the axis of the crank, by 
systems of wheels and pinions. 



190. In]manufacturing machinery, the motions are taken » 
off in the same manner. It would be tedious, nay impossi- I 
ble, to recite every particular case of this sort, we shall i 
therefore limit ourselves to the spinning of cotton. In 

this branch of manufacture, it is estimated, that each horse 
power will drive 200 throstle spindles, or 1000 mule spin- 
dles, and perform all the work of preparing the cotton for 
them. 

Those subjects which appear to require more full illustra- 
tion in this work, are the propulsion of vessels, and the 
motion of carriages upon rail-roads. 

191. Vessels are, generally speaking, propelled through 
the water, by the action of paddle-wheels, and this, 
although the simplest and most obvious method, is also 
that which has hitherto been found preferable to any that 
has been proposed. To set this apparatus in motion, it is 
merely necessary to place it upon the axis of the crank of a 
steam engine, whether furnished with a lever beam, or of 
the simpler form exhibited upon pi. VII., in which that part 
of the older engines is suppressed. It will thus acquire a 
velocity equivalent to a complete revolution, during a com- 
plete ascent and descent of the piston, or during two 



STEAM-BOATS. 261 

strokes of the engine. The force exerted by the wheels 
depends upon the velocity with which they strike the 
water, which is obviously the difference between their own 
velocity of rotation and the progressive velocity of the 
vessel ; upon the immersed area of the paddle ; and the 
fluid resistance of the water. The velocity of the vessel 
will depend, upon the force with which the wheel tends to 
impel it, on the one hand, and the resistance the water 
opposes to its progressive motion on the other. 

To determine the velocity that a given engine will give 
to a vessel, and the conditions under which it may produce 
a maximum of effect, is evidentally a problem of great 
complexity. We do not conceive that it has ever been 
solved in a manner perfectly satisfactory, either in theory 
or practice, nor do we hope to give any important 
addition to the knowledge of this subject, from our own 
investigation. 

The resistance of fluids, to bodies moving in them, is 
governed by laws that are far from simple, and these affect 
the motion both of the vessel and the wheels ; while in the 
estimate of the action of the wheels, the velocity of the 
vessel comes in as an essential element, and this can hardly 
be determined accurately by any preliminary investigation. 
The speed of a steam engine is limited, by the quantity of 
vapour of the proper tension that the boiler can furnish, 
and with this, that of the paddle is connected, within 
restricted limits, unless a system of wheels and pinions be 
resorted to, which is not the case in American steam-boats. 

Even the simplest point concerned in the investigation : 
namely, the velocity of the wheel through the water, at 
which a maximum effect would be produced, does not 
appear to have been solved. 



# 



262 NAVIGATION BY STEAM. 

192. The researches of Bossut gives us the laws, which 
fluids follow in impinging against solid bodies. These are 
as follows, viz. 

1. With equal surfaces similarly inclined to the fluid, the 
resistances are nearly" proportioned to the squares of the 
velocities ; 

2. With equal velocities, and equal inclinations of the 
surfaces to the fluid, the resistances are proportioned to 
the areas of the surfaces ; 

3. With equal velocities and equal surfaces, the resist- 
ances are nearly proportioned to the squares of the sines 
of the angles of inclination, until the angle of incidence 
diminish to 50*^ ; beyond this the diminution is more rapid. 

4. The measure of the action of a fluid upon a plane 
surface, is equal to the weight of a column of water, whose 
height is that whence a heavy body must fall to acquire the 
velocity. 

The action of paddle-wheels are governed by laws that 
cannot difl'er much from these, which hold good in the case 
of simple impact, because the circumstances which influ- 
ence the motion of bodies moving in masses of fluids, and 
which we shall state hereafter, have little efiect upon pad- 
dles. 

In bodies whose resistance varies with the square of the 
velocity, the theorem of Parent shews, that a maximum of 
effect is attained when the velocity of action is one-third of 
the greatest attainable velocity. 

193. To apply this principle to the case before us, we 
conceive, that a course must be taken analogous to that 
which is employed, in investigating the maximum action of 
the power of men and of animals. Here the speed that 
can be acquired and kept up by a violent exertion, is never 
taken into view, andjhat isjassumed, as th« basis of the 



NAVIGATION BY STEAM. 263 

calculation, which can be persevered in, for the number of 
hours in which the force can be usefully applied per day. 
In other words, the limit of ordinary application, within 
which the law of regular action holds true, is made use of. 
And so in investigating the action of water upon bodies, we 
would assume that the velocity, at which the resistance be- 
gins to increase at a rate obviously greater than the square 
of the velocity, must be taken as the limit. 

If this velocity be ascertained, the speed at which the 
maximum of effect is attained, is one-third of it. The great- 
est speed of a vessel will be this velocity, or three times as 
great as that with which the paddle-wheels move through 
the water when acting at a maximum ; and as the effective 
velocity of the wheels, is the difference between their own 
rate of rotation and the velocity of the vessel through the 
water, the relation between the most rapid motion that can 
be given to a vessel, and that with which its paddles should 
move to produce a maximum effect, is as three to four. 

194. The greatest speed of vessels, and consequently 
the maximum velocity of paddle-wheels, may be exa- 
mined, either by the aid of theory, or ascertained by actual 
experiment. For the theoretic investigation we shall 
have recourse to principles of Don George Juan. 

It is conclusively shewn by this author, that the resist- 
ance, which opposes the motion of bodies moving in fluids, 
may be divided into three parts. 

1. A resistance growing out of the disturbance of the 
conditions ol equilibrium, and arising from the friction of 
the fluid. This is a constant force. 

2. The fluid resistance proper, which varies with the 
square of the velocities. This has so small a co-efficient, 
that it is insensible at small velocities, but increasing with 
their squares, it speedily becomes the most important, and 



264 NAVIGATION BY STEAM. 

the first bears then so small a relation to it, that at mean 
velocities this need alone be taken into view. 

3. The wave raised in front of the moving body, and a 
want of support from behind, growing out of the space 
which the body leaves unfilled behind it, when the velocity 
becomes great. The mere resistance, growing out of these 
causes, increases with the fourth power of the velocities, but 
in addition, the weight of the body must be raised upon an 
inclined plane, and hence will arise a limit beyond which 
the velocity of no vessel can be carried. 

At small and mean velocities, this species of resistance 
is wholly insensible, but it finally becomes, in consequence 
of its rapid increase, the most important of the three. It 
is when this occurs that we would fix the IMt of the speed 
that can be advantageously given to a vessel, or with which 
a paddle can be impelled. 

195. To determine the limit experimentally, we must 
have recourse to what is observed in the motion of ships. 

The maximum speed of fast sailing vessels is usually 
taken at 12 geographical miles per hour, but is said that 
there are instances of vessels having reached 15, and steam- 
boats have recently been constructed which a little exceed 
the former limit. We shall, however, assume 12 geo- 
graphical miles, or 13.2 English miles as the limit. This is 
equivalenttol9.5feetper second, one-third of this is 6. 5 feet, 
which is, according to our principles, to be taken for the 
maximum relative velocity of a steam-boat's paddle-wheel. 

196. To determine the power required to propel the 
paddle with this velocity, it is to be considered, that the 
measure of force depends not only the resistance over- 
come, but the velocity with which it is conquered. Hence 
the resistance estimated above as being equal to the weight 



NAVIGATION BY STEAM. 265 

of a column of water whose base is the area of the paddle, 
and whose height is that whence a heavy body must fall to 
acquire the velocity, is to be multiplied by the velocity per 
minute, and the product divided by the weight raised by 
the unit of power in the same space of time. 

The height due to a given velocity is found by dividing 
the square of the velocity per second by the constant 
number 64. 

The unit of power is 32,0001bs. raised one foot high, but 
this is probably reduced in the machine itself, as we have 
heretofore seen, to 24,000lbs. Hence we would have the 
following rule : 

Multiply together the cube of the relative velocity, the num- 
ber of seconds in a minute, the weight of a cubic foot of water 
in lbs., (62 1) and the area of the paddle in feet, divide the 
product by the constant number 24,000 multiplied by the con- 
stant number 64, the quotient is the horse power. 

The other rules deduced from theory, are as follows : 

In the same vessel, and with a constant relation between 
the area of the paddle-wheels and the transverse section 
of the vessel, the velocities are as the cube roots of the 
powers of the engines. # 

The relation between the velocity of the wheels and of 
the vessel is constant, so long as the ratio between their 
surfaces remains the same. 

197. If we apply the rule we have just given, to the case 
of a paddle-wheel working at a maximum or with a velo- 
city of 6.5 feet per second, we shall find that each horse 
power of the engine should be capable of impelling a pad- 
dle of half a square foot. But a paddle does not act during 
the time of its immersion in the water with equal intensity, 
and although no loss of power might arise from this cause, 
the obliquity of its action applies a part of the force to re- 

34 



266 NAVIGATION BY STEAM. 

sistances, that do not assist in propelling the vessel. Thus, 
on entering the water, a part of the force is applied to lift 
the wheel from its axis and on quitting the water to press 
it down. In addition, a quantity of water is raised upon 
the paddle, a part of whose weight acts in direct opposition 
to the moving power. The loss growing out of these 
causes can only be investigated experimentally. We shall 
attempt this from a comparison of the circumstances of the 
steam-boats North- America, and President. The former 
navigates the Hudson River, and is remarkable for a speed 
that has hitherto never been equalled, by any other steam 
vessel ; the latter plying between New-York and Provi- 
dence, it has been found in her construction, necessary to 
preserve stability as well as to obtain speed, and if her ve- 
locity be less than that of the former, she still combines the 
two qualities of speed and safety, in a degree superior to 
any vessel we are acquainted with. 

The particulars necessary for our purpose in relation to 
the President, are as follows, viz : 

Breadth of beam, 32 ft. 6 in. 

Draught of water, 9 ft. 

Diameter of Water-wheels, . . 22 ft. 

Length of bucket, 10 ft. 

Depth of do 3 ft. 6 in. 

She has two engines of the following dimensions : 

Diameter of Cylinder, .... 4 ft. 

Length of Stroke, 7 ft. 

Number of double strokes or complete revolutions of 
paddle-wheel per minute 21. When but one engine works 
the number of revolutions of the single wheel on which it 
acts are reduced to 17^. 

The average passages to Providence have been perform- 
ed, [when both engines acted, in 15i hours ; when but one 
was used, in 19i. 



NAVIGATION BY STEAM. 267 

The distance between New-York and Providence is usu- 
ally estimated at 210 miles ; carefully measured, however, 
upon a map, it is found to amount to no more than 160 
nautical, or 184.3 English miles. From these data, the 
average velocity of the boat through the water is very 
nearly 12 miles per hour, or 17.6 feet per second ; the 
average relative velocity of the wheel 6.5 feet per second, 
when both wheels and engines were in motion ; the ave- 
rage velocity of the boat when but one engine worked, be- 
comes 9.45 miles per hour, or 13.86 feet per second ; the 
relative velocity of the wheel 6.3 feet per second. 

The wheels, therefore, move with a relative velocity al- 
most identical with that which our the'ory has shown to 
correspond to a maximum effect. But the actual effect is 
far beneath the rule we have laid down. Estimated from 
a comparison with other condensing engines, those of the 
President would have each a nominal power of about 70 
horses, which in consequence of the rapidity of their action 
is increased to about double ; but by the rule on page 1 38, 
the power of each of the engines is that of 160 horses. As 
each paddle has a surface of no more than 35 square feet, 
each horse power drives no more than 0.22 feet of paddle, 
or less than one-fourth of a square foot. And it would 
appear from comparing the relative .velocities in these two 
cases, as if, in this vessel, the proper ratio between the 
moving power and the paddle had been attained. 
The North- America has the following dimensions : 

Breadth of beam, 30ft. 

Draught of water, 5 ft. 

Diameter of Water-wheel, . . . 21ft. 

Length of bucket, 13-ft. 

Depth of do 2 ft. 6 in. 

She has two. engines of the following dimensions : 

Diameter of Cylinder, .... 44i in. 



268 NAVIGATION BY STEAM. 

Length of Stroke, 8 ft. 

Double Strokes per minute, 24 

The estimate of her speed furnished by her owners, is 
19.8 feet per second, or exceeds our theoretic limit by 
three-tenths of a foot. The relative velocity of the wheel 
is 6.6 feet per second, exceeding our theoretic limit one- 
tenth of a foot. The relation between the velocities of the 
boat and the wheel is as 3 to 4, or identical with that 
chosen by us as the most advantageous. 

The power of each of the engines estimated by the rule 
on page 138, is 186 horses, the area of each paddle 32^ ; 
and hence each horse power propels no more than 16 hun- 
dredth parts of a square foot through the water. 

The velocity of the wheel is, however, greater than that 
of the President in the ratio of 6.3 : 6.6, or of 21 to 22 ; 
which makes the comparison more favourable than would 
at first appear, to the North- America. For, conceiving 
the wheels of the former to work to the greatest possible 
advantage, each horse power would, at the increased rela- 
tive velocity the latter has, propel no more than one-fifth 
of a square foot of paddle. 

The powers of the engines of both boats, as estimated 
by us, far exceed what would usually be ascribed to them 
from a mere consideration of their dimensions. Those of 
the President being of the size of condensing engines usu- 
ally estimated at 110 horse powers; those of the North- 
America, at 98 horse powers. This difference arises from 
the great speed ^ith which they are driven ; it being usual 
to give no more velocity to the piston of a condensing 
engine than about 200 feet per minute, while that of the 
North-America has 384 feet, and that of the President 
336 feet. 

The near coincidence of the actual performance of these 
boats with our theory, except in one respect, is a tolerable 



NAVIGATION BY STEAM. 269 

warrant for its accuracy. The point in which this differ- 
ence occurs, is the area of paddle that can be driven by- 
each horse power of engine. Our rule on page 265 
would make this force equivalent to move half a square 
foot with the velocity of 6.5 feet per second, while in the 
case of the President the actual performance, reduced to 
that velocity, is no more than one-fifth of a square foot, 
while in the case of the North-America it falls as low as 
one-sixth. The disturbing causes that effect this variation 
from the theory are obvious, and have been explained, but 
it is not easy to reduce them to calculation. 

198. We have seen that the resistance sustained by a 
body moving in a fluid is proportioned, to the square of its 
velocity, and the area of its section. 

The moving force, necessary to give a vessel a given 
velocity, must therefore, as has also been stated, be equal 
to this resistance multiplied by the velocity, or propor- 
tioned to the cube of the velocity ; and in similar vessels 
the resistance is proportioned to the square of one of the 
homologous dimensions. 

Thus to obtain double the velocity in a given vessel, and 
with given wheels, eight times the force must be employed, 
and so on. 

But as the space passed over in a given time is |)ropor- 
tioned to the velocity, the actual expenditure of power, 
in performing a given distance, is proportioned to their 
squares of the velocities. ' 

These laws, however, are only true when the weight of 
the engine is considered as constant, but as this increases 
in a greater ratio than the power, it will make the acquisi- 
tion of great velocities still less advantageous. 

An obvious advantage will be gained by increasing the 
size of the vessels, for the resistances vary as the square of 



270 NAVIGATION BY STEAM. 

similar dimensions, while the tonnage increases with their 
cubes. 

It has been imagined by some, that the motion of steam- 
boats was different in a current from what it is in still water. 
This, however, cannot be the case, unless it be so rapid 
that its slope becomes an important element, forming an 
inclined plane up which the weight is to be lifted. This 
conclusion is obvious from the following considerations. 
When a vessel is in a current, and the propelling force 
ceases to act, she speedily acquires the velocity of the 
fluid, and is relatively at rest in respect to it. If the pro- 
pelling force be steam applied to wheels, and they be set 
in motion, the action upon the fluid is precisely the same 
as if no current existed, and hence the velocity through 
the water will _be the same as when the fluid is at rest. 
Thus then the velocity, in respect to the shore, will be 
the sum or difference, of the velocity the vessel would 
have in still water, and that of the stream. The case is of 
course widely different, when the force is applied by chains, 
or other connexion, with a fixed point upon the shore. 

199. The next consideration in respect to paddle-wheels 
is their diameter. This is determined by means of the 
velocity that it is intended to give the circumference, com- 
pared with the velocity of the piston ; the wheel being 
attached to the crank will make half a revolution for each 
stroke of the piston. Hence in this mode of gearing the 
wheels, great velocities can only be attained by a propor- 
tionate increase of the diameters. This is attended with 
several practical inconveniences, first in a great increase of 
the weight, and secondly, in raising the height of the centre 
of gravity. The action of a paddle depends, as has been 
shown, upon its relative velocity, but when the paddles of a 
wheel act in succession, the water will follow in the wake of 



NAVIGATION BY STEAM. 271 

the first which acts, and the second may, if it succeed at too 
short an interval, impinge upon water that is already in mo- 
tion. For this cause, the paddles upon the wheels should not 
be more numerous than is just sufficient to keep up a con- 
tinuous action. The proper arrangement, for this reason, is 
such, that when one paddle is vertical, the preceeding one 
shall be just issuing from, and the succeeding one just 
entering the water. 

When paddle wheels impinge against the water in an 
oblique direction, they sustain a sudden shock, when the 
interval is as great as we have pointed out ; the reaction 
of this sudden resistance upon the engine is injurious, and 
and it checks and destroys the accumulation of power the 
water-wheel might otherwise attain, and distribute, upon 
the principle of the fly-wheel. Hence in the early steam- 
boats, fly-wheels driven with greater velocity than the 
paddle-wheels, were found of great value ; and even in the 
rapidly moving boats of the present day, where the velocity 
and weight of the paddle-wheels enable them to answer 
the purpose of a fly-wheel, these shocks are not without 
an injurious eff'ect. 

Two different methods have been proposed to remedy 
this defect. 

In some English steam-boats, the paddles have been 
placed obliquely upon the circumference of the wheel, but 
still perpendicular to a plane tangent to it ; their inclina- 
tion to the vertical plane, therefore, remains the same as 
in the usual form, but they enter the water by an angle, 
instead of striking with one side, and hence do not experi- 
ence the shock of which we have spoken. 

There is, however, a defect which more than compen- 
sates any advantage to be derived from this arrangement. 
The wheels act in directions inclined to the plane of the 
vessel's keel, and thus a part of their power is exerted to 



272 NAVIGATION BY STEAM. 

press the vessel in a lateral direction ; and although the 
two wheels mutually neutralize this part of each other's 
action, the whole of the force exerted in this direction is 
wasted. 

A better arrangement has been introduced into his 
steam-boats by Mr. R. L. Stevens. The wheel is triple, 
and may be described, by supposing a common paddle- 
wheel to be sawn into three parts, in planes perpendicular 
to its axis. Each of the two additional wheels, that are thus 
formed, is then moved back, until their paddles divide the 
interval of the paddles on the original wheel, into three 
equal parts. 

In this form, the shock of each paddle is diminished to 
one-third of what it is in the usual shape of the wheel ; 
they are separated by less intervals of time, and hence ap- 
proach more nearly to a constant resistance; while each 
paddle following in the wake of those belonging to its own 
system, strikes upon water that has been but little dis- 
turbed. 

Another loss in the application of the power arises, as we 
have seen, from the water that is lifted by the paddles as 
they pass out of the water. But the loss is not equal to 
the whole weight lifted, for this water will already have 
have acquired a velocity of rotation that will diminish the 
pressure on the paddle, and as the paddle is oblique, the 
actual pressure may be resolved into two forces, one of 
which retards the motion of the wheel, and is lost, while 
the other acts horizontally to propel the vessel. This loss 
will of course be least in large wheels, if the immersion of 
the bucket be constant. The larger the wheel the less 
will be the weight of the water lifted. 

The paddle is not immersed wholly in the water except 
when nearly in its vertical position. Hence it does not 
exert a constant force to propel the vessel, but as the ex- 



NAVIGATION BY STEAM. 273 

penditure of power from the engine will follow the law of 
the area, no loss arises from this cause. But the inclina- 
tion of the paddle is besides constantly varying, and while 
the water opposes a resistance perpendicular to the surface 
of the paddle, depending upon the area immersed and the 
square of the velocity ; only that part of this resistance, 
which, when decomposed, is parallel to the surface of the 
water, acts to propel the vessel, the rest is wasted upon the 
vessel, whose weight is alternately lifted and forced down- 
wards. It is to this obliquity of action that the great differ- 
ence between the area that theory would assign to paddles, 
and those which have been used in practice, is more par- 
ticularly to be attributed. We have seen that these several 
causes united, have reduced the area of paddle propelled 
by each horse power of engine, in the most advantageous 
case we have considered, to about one-fifth part of a square 
foot. 

A steam vessel is set in motion with a velocity that gradu- 
ally increases, until it become uniform. At this time the 
resistance of the water to the motion of the wheels, exactly 
balances the progressive motion of the vessel. Hence, 
if we knew the relation between the laws by which the re- 
sistance to plane surfaces, and to those of the figure of a 
vessel are governed, we might determine the proportion 
which ought to exist, between the area of the paddle, and 
that of the midship frame of the vessel. Experiments 
made by the Society of Arts in London, appear to show, 
that when a solid of small size is fashioned into the figure 
of a vessel, the resistance was not more than |th of that 
which opposes a plane surface. Other observations make 
the resistance to good models vary from ith to yVth. 

But observation on a large scale gives far more favoura- 
ble results. In the case we have above quoted of the steam- 
boat President, the resistance to the transverse section of 

35 



274 



NAVIGATION BY STEAM. 



the vessel is no more than ^^th part of that incurred by the 
wheels, when both engines act ; while, when but one acts, 
it falls as low as ^h^h. In the North- America, it appears 
to be no more than -^\d. No possible danger, then, can 
arise, in assuming, that in a vessel of a good model, the re- 
sistance to the progressive motion falls as low as y\th part 
of that which acts upon the paddles. If, then, we assume 
for the relation between the absolute velocities of the boat, 
and the wheel, when working to the greatest advantage, the 
proportion already stated of 3 : 4 ; the most advantageous 
size of paddles will be such that the area of each should be 
one-fourth of that of the midship frame of the vessel, or the 
sum of those which act at a time, on both wheels, one-half 
of that quantity. If the engine be so constructed as to give 
the paddle-wheel a rotary velocity of 26 feet per second, 
the boat will acquire a velocity of 13.2 miles per hour. 
This, with other relations and velocities calculated upon the 
same principles, are arranged in the following table. 

Table of the Velocities of Steam-boats and their paddles, 
when the latter act at a maximum, at different ratios 6c- 
tween the areas of the paddles, and the midship frames. 



r 




■ ■ ■ — ^ 


Ratio of 
Areas. 


Rotary Velocity 

of Wheel 

per secoad. 


Velocity of Boat 
per hour, 
in miles. 


1 
2 


26. 


' 13.2 


1 


25.2 


12.57 


_3_ 

I 


22.5 


10.73 


1 

4 


21. 


9.78 


t\ 


19.5 


8.88 


2 

20 


17.7 


7.78 


1 

1 


15.3 


6.00 


I 
1 3 


14.6 


5.5 



These results are, of course, only approximative, and 
will be affected in a very material degree by the figure of 
the vessel, and various other circumstances that no theory 
can take into account. 



NAVIGATION BY STEAM. 275 

200. Our practical rules may now be summed up and 
recapitulated, as follows, viz. 

1. The relative velocity of the circumference of the 
wheel, should be, in all cases, six and a half feet per 
second. 

2. Each horse power of engine, calculated according to 
the rules on page 138, will drive a paddle of the area of 
one-fifth part of a square foot with this velocity. 

3. The maximum absolute velocity of a paddle, to give 
the greatest velocity a boat can attain, is 26 feet per 
second. 

4. In a vessel of good model, these velocities may be 
attained, when the relation between the area of the midship 
frame of the vessel, and that of the paddles of both wheels, 
is as two to one. 

5. With other relations between these areas, the veloci- 
ties are those given in the preceding table. 

201. The steam engine, such as has been described in 
Chapter V., requires several modifications to suit it for 
the purpose of propelling boats. When placed in the body 
of the vessel, that form represented in PI. VII., in which 
the great working-beam is suppressed, and two connect- 
ing-rods adapted to the piston by a cross-head, is the best. 
But when two engines placed upon the wheel-guards are 
employed, the beam must be retained. The cold-water 
cistern would load the vessel with an enormous weight, and 
hence the condenser is not immersed in water ; the hot- 
water cistern is, generally speaking, set upon the top of 
the air-pump ; and the delivering-door is a conical valve 
surrounding the air-pump rod. Water for condensation is 
supplied by a pipe, passing through the bottom of the boat 
and rising above the level of the external mass of fluid ; the 
injection-cock is below this level, and the water is forced 



<< 



276 HISTORY OF 

into the condenser, by virtue of the difference of level. The 
vraste hot water passes out by a similar pipe. These pipes 
are called standing* pipes, and they are represented on 
PI. VII., dXhh and I ; h h being the pipe adapted to the 
condenser, which it supplies through the injection-cock i, 
and I being the pipe through which the waste hot water is 
discharged, from the cistern on the top of the air-pump H. 
A hand force-pump K, is employed to fill the boiler at first, 
and it is afterwards supplied by a force-pump /. 

Another very important modification consists in the size 
of the valves and steam-pipes. It has already been seen, 
that in some cases, when steam acts expansively, the area 
of the nozzle should be increased ; but in steam-boats, the 
great velocity required for the wheels is usually gained, not 
by gearing, but by increasing the velocity of the piston. 
This can only be attained by affording a passage for an in- 
creased flow of steam. This method of increasing the 
speed has this advantage, that velocity, and in consequence 
power, is gained without increasing the weight of the en- 
gine. 

203. The application of steam to the propulsion of ves- 
sels, appears to have been among the very first ideas that 
suggested themselves, to the inventors or improvers of the 
engine, Worcester, in the quotation that we have made 
from the " Century of Inventions," speaks of the capacity 
of his invention for rowing. Savary proposed to make the 
water raised by his engine turn a water-wheel within a ves- 
sel, which should carry paddle-wheels acting on the out- 
side ; and Watt, as we are well assured by a personal 
auditor, stated in conversation, that had he not been pre- 
vented by the pressure of other business, he would have 
attempted the invention of the steam-boat. Newcomen 
alone, gave, as far as we can learn, no intimation -of any 



STEAM NAVIGATION. 277 

such design ; and this we are rather to take as an evidence 
of his correct appreciation of the powers of his engine, 
than as arising from any want of ingenuity. In truth, be- 
fore the time of Watt, no modification under which steam 
was applied to useful purposes, would have been able to 
propel vessels successfully. Even with all his improve- 
ments, the fuel is a great load, and its carriage no small 
difficulty ; but, before he lessened its consumption so ma- 
terially, it would have been hardly possible for a vessel to 
carry enough of combustible matter, except for very short 
voyages. 

Previous in date to all these persons, recent discoveries 
have brought to light an ancient record in which we have 
the description of a vessel propelled by steam, in a manner 
that obtained the suffrages of the witnesses. 

Blasco de Garay, an officer in the service of the Empe- 
ror Charles V., made, at Barcelona, in the year 1543, an ex- 
periment on a vessel, which he forced through the water by 
apparatus, of which a large kettle filled with boiling water, 
was a conspicuous part. If this be true, and we have no 
reason to doubt the authenticity of the records, De Garay 
was not only the first inventor of the steam-boat, but the 
first who was successful in applying a steam engine to use- 
ful purposes. He was, however, too far in advance of the 
spirit of his age, to be able to introduce his invention into 
practice, and even the recollection of his experiment had 
been lost, until the record was accidentally detected among 
the ancient archives of the province of Catalonia. This 
experiment was, therefore, without any direct practical 
result, neither did it produce any effect in facilitating the 
researches of subsequent inquirers, and may therefore be 
considered rather as a matter of curious antiquarian re- 
search, than as deservedly filling any space in the history 
of the steam-boat. 



378 HISTORY OF 

English authors have also raked up from oblivion a pa- 
tent granted in the year 1736, to a person of the name of 
Jonathan Hulls. He, however, never made even an act- 
ing model of his invention, and the prime-mover itself was 
at the time in a state far too imperfect to have permitted its 
being successfully used, in the manner proposed by Hulls. 
So far then, from classing this among ingenious and profit- 
able improvements, we should rather be inclined to rank it 
among those, which, from their obvious impracticability, 
merit the oblivion into which they instantly fall. 

The paddle wheel, it has been stated, is the only appara- 
tus that, when worked by steam, has been found complete- 
ly successful in propelling vessels. The use of this for 
such a purpose, but set in motion by other prime-movers, 
is of remote antiquity, and was from time to time again 
brought forward, used for a season, and again abandoned. 

Among these attempts, may be mentioned a boat con- 
structed on the Thames by Prince Rupert, whose action 
was witnessed by Papin, by Savary, and probably by Wor- 
cester. So far as regards the antiquity of the method, 
Stuart quotes manuscripts from the library of the King of 
France, from which he states it was ascertained, that during 
one of the Punic wars, a Roman army was transported to 
Sicily, upon vessels moved by wheels worked by oxen. 
The use of a water-wheel, in a manner the reverse of that 
in which it was employed to propel machinery, is almost 
too obvious to be entitled to the character of invention ; it 
was, therefore, only necessary that the necessity for their 
use should exist, and their introduction would have follow- 
ed as a matter of course. 

It was, however, long questionable whether they could 
be used to advantage when attached to a steam engine, and 
in the earlier experiments, the blame appeared to fall upon 
them, rather than upon the imperfections of the engine, or 



STEAM NAVIGATION. 279 

the unskilful, and unartistlike manner in which they, and 
the rest of the apparatus, were adapted to the vessels. 

We have stated that Watt's engine was the first possess- 
ed of sufficient powers to be used to advantage in vessels. 
This is not merely an inference from what can be observed 
in the practice of the present age, but was in 1753, made 
a matter of mathematical proof by Bornouilli, in a memoir 
that gained a prize ofi'ered by the French Academy of 
Sciences. He, however, expresses his opinion too broad- 
ly, applying his inference rather to the power of steam it- 
self, than the mode in which it was then commonly 
applied. 

Still there were some, who, not aware of the defects of 
the prime-mover, continued to seek for the means of apply- 
ing it to vessels. Among these may be named Genevois and 
the Comte d'Auxiron. The former, whose attempt dates 
as early as 1759, is chiefly remarkable for the peculiarity 
of his apparatus, which resembled in principle the feet of 
aquatic birds, opening when moving through the water in 
one direction, and closing on its return. The latter made 
an experiment in 1774, but his boat moved so slowly and 
irregularly, that the parties at whose expense the trial was 
made, at once abandoned all hopes of success. 

In 1775, the elder Perrier, afterwards so celebrated as 
the introducer of the manufacture of steam engines into 
France, made a similar attempt, which was equally unsuc- 
cessful. But not discouraged, and ascribing his failure to 
the use of paddle-wheels, he applied himself for some years 
afterwards to the search for other substitutes for oars. It 
does not appear, however, that he made any valuable dis- 
covery. 

The Marquis de JoufFroy continued the pursuit of the 
same object. His first attempts were made in 1778, at 
Baume les Dames, and in 1781, he built upon the Saone, a 



280 WATT. 

steam-vessel 1 50 feet in length and 1 5 in breadth. In 1 783, 
his experiment became the subject of a report made to the 
French Academy of Sciences, by Borda and Perrier. The 
report is said to have been favourable. We have seen that 
the double-acting engine of Watt was not made public be- 
fore 1781, and that it was not until 1784 that it received 
those improvements, by which it was fitted to keep up a 
continuous and regular rotary motion. No previous engine 
having the necessary properties, we feel warranted in re- 
jecting all attempts prior to the former date, as premature, 
in attempting to perform that to which the means, in the 
possession of the projectors, were inadequate. 

We are to look to our own country, not only for the first 
successful steam-boat, but for the very earliest researches 
into the subject, after the improvement of the engine by 
Watt, had rendered success attainable. The very nature 
and circumstances of the United States appeared to call for 
means of conveyance, different from those which are em- 
ployed in other countries. Our whole coast is lined by 
bays and rivers, by the aid of which a safe parallel naviga- 
tion, might, at small expense, be extended from one extre- 
mity of the Union to the other, but which, land-locked, and 
protected from the winds, is at some seasons tedious to 
the ordinary methods. Still more recently, the Mississippi 
and its innumerable branches, have become the seat of 
flourishing settlements, separated from the Atlantic coast 
by ridges of barren mountains, and almost inaccessible 
from the Gulf of Mexico, by either sails or oars, in conse- 
quence of the rapidity of the stream. Our population, 
with the wants and curiosity of the highest civilization, is 
still so scattered over a vast region, as to demand rapid 
means of communication, and great foreign importations. 
These wants could not have been satisfied, nor this active 
curiosity gratified, by any means yet discovered, except the 



RUMSEY — FITCH. 281 

steam-boat. The earlier projectors appear, however, 
rather to have reference to the prospective state of our 
country than to circumstances which existed at the mo- 
ment of their attempts. Hence we shall find, that they 
soughtifribreign countries, the encouragement, the wealth 
of their native land was inadequate to afford. 

Rumsey and Fitch were cotemporaneous in their re- 
searches. Both attempted to construct steam-boats as 
early as the year 1783, and models of both their contrivan- 
ces were exhibited in 1784, to General Washington. Rum- 
sey's was the first in date of exhibition, but Fitch was first 
enabled to try his plan upon a scale of sufficient magni- 
tude ; for, in 1785, he succeeded in moving a boat upon the 
Delaware, while Rumsey had not a boat in motion upon 
the Potomac before 1786. 

Fitch's apparatus was a system of paddles ; Rumsey at 
first used a pump, which drew in water at the bow, and 
forced it out at the stern of his boat. The latter afterwards 
employed poles, set in motion by cranks on the axis of the 
fly-wheel of his engine, which were intended to be pressed 
against the bottom of the river. About the date of these 
experiments. Fitch sent drawings of his apparatus to Watt 
and Bolton, for the purpose of obtaining an English pa- 
tent ; and in 1789, Rumsey visited England upon the same 
errand. The former was not successful in obtaining 
patronage, but the latter, by the aid of some enterprising 
individuals, procured the means to build a vessel on the 
Thames, which, however, was not set in motion until after 
his death, in 1793. 

Fitch's boat was propelled through the water at the rate 
of four miles per hour. We may now reasonably doubt, 
whether paddles would have answered the purpose 
upon a large scale, for more than one experiment on 
this principle has since been tried, and without success. 

36 



282 MILLER. 

The method of Rumsey is more obviously defective, and 
we need not wonder that it was followed by no valuable 
results. 

Next in order of time to Fitch and Rumsey, we find Mil- 
ler, of Dalswinton in Scotland. This ingenious gentleman 
had, as early as 1787, turned his attention to substitutes 
for the common oar, and had planned a triple vessel pro- 
pelled by wheels. Finding that wheels could not be made 
to revolve with sufficient rapidity, by men working upon a 
crank, the idea of applying a steam engine was suggested 
by one of his friends, and an engineer of the name of Sym- 
ington, employed by him to put the idea into practice. The 
vessel was double, being an experimental pleasure boat on 
the lake in his grounds at Dalswinton. The trial was so 
satisfactory, that Miller was induced to build a vessel sixty 
feet in length. This was also double, and it is asserted 
that it was moved by its engine along the Forth and Clyde 
Canal at the rate of seven miles per hour. The boat, the 
wheels, and the engine, were, however, so badly propor- 
tioned to each other, that the paddles were continually 
breaking, and the vessel suffered so much by the strain of 
the machinery as to be in danger of sinking, and Miller 
found it unsafe to venture into any navigation of greater 
depth than the Canal. The apparatus was, therefore, re- 
moved and laid up, and here the experiments of Miller 
ceased. He himself appears evidently to have considered 
this experiment an absolute failure, and ascribed the blame 
to the engineer. We have to remark, that the double boat 
used by Miller, was a form ill suited to the purpose ; in 
the ferry boats of that structure, introduced by Fulton into 
this country, the resistance growing out of the dead water 
included between the two hulls, has been found such, that 
they have been gradually abandoned, and single vessels 
substituted. 



STEVENS — STAN HOPE. 283 

John Stevens, of Hoboken, commenced his experiments 
on steam navigation in 1791. Possessed of a patrimonial 
fortune, and well versed in science, he was at the time, 
wanting in the practical mechanical skill that was necessary 
to success ; he was hence compelled, at first, to employ men 
of far less talent than himself, but who had been educated 
as practical machinists. His first engineer turned out an 
incorrigible sot ; his second became consumptive, and died 
before the experiment was completed. Stevens then re- 
solved to depend upon his own resources, and built a work- 
shop on his own estate, where he employed workmen under 
his own superintendence. In this shop he brought up his 
son, Robert L. Stevens, as a practical engineer, to whom 
many important improvements in steam navigation, and the 
most perfect boats that have hitherto been constructed, are 
due. 

During these experiments, Stevens invented the first 
tubular boiler ; and his first attempts were made with a 
rotary engine, for which, however, he speedily substituted 
one of Watt's. With various forms of vessels, and difi"erent 
modifications of propelling apparatus, he impelled boats at 
the rate of five or six miles per hour. They were in truth 
more perfect than any of his predecessors', but did not 
satisfy his own high raised hopes and sanguine expecta- 
tions. These experiments were conducted at intervals up 
to the year 1807, and much diminished his fortune. We 
must, however, pass from the detail of them, and the no- 
tice of the parties who became concerned with him, in order 
to speak of what was doing in Europe in the meantime. 

The Earl of Stanhope, in 1793, revived the projec:^ of 
Genevois, for an apparatus similar to the feet of a duck. 
It was placed, in 1795, in a boat furnished with a powerful 
engine. He was, however, unable to obtain a velocity 
greater than three miles per hour. While engaged in these 



284 LIVINGSTON. 

experiments, he received a letter from Fulton, who pro- 
posed the use of paddle-wheels ; and it is probable that his 
neglect to listen to this suggestion caused a delay in the 
introduction of the steam-boat of at least twelve years ; for 
we cannot doubt that the ingenuity of Fulton, backed by 
the capital and influence of Lord Stanhope, would have 
been as successful then, as it was on a subsequent occa- 
sion. 

In the year 1797, Chancellor Livingston, of the state of 
New- York, built a steam-boat on the Hudson River. He 
was associated in this enterprize with a person of the name 
of Nisbett, a native of England. Brunei, since distinguish- 
ed for the block machinery, and as engineer of the London 
Tunnel, acted as their engineer. In the full confidence of 
success, Livingston applied to the legislature of the state of 
New-York, for an exclusive privilege, which was granted, 
on condition that he should, within a year, produce a vessel 
impelled by steam, at the rate of three miles per houTi 
This they were unable to effect, and the project was drop- 
ped for the moment. 

In the year 1800, Livingston and Stevens united their 
efforts, and were aided by Mr. Nicholas Roosevelt. Their 
apparatus was a system of paddles resembling a horizontal 
chain pump, and set in motion by an engine of Watt's con- 
struction. We now know that such a plan, if inferior to 
the paddle-wheel; might answer the purpose ; it, however, 
failed, in consequence of the weakness of the vessel, which, 
changing its figure, dislocated the parts of the engine. 
One of the workmen in their employ suggested the use of 
the paddle-wheel in preference, but, as Stevens candidly 
states, their minds were not prepared to expect success 
from so simple a method. 

Their joint proceedings were interrupted by the appoint- 
ment of Chancellor Livingston to represent the American 



SYMINGTON — EVANS. ^5 

government in France, but neither he nor Stevens were 
yet discouraged ; the latter continued to pursue his experi- 
ments at Hoboken, while the former carried to Europe 
high raised expectations of success. 

It has been stated that Symington was employed by Mil- 
ler, of Dalswinton, as his engineer ; we have now to record 
an attempt made by him under the patronage of Lord 
Dundas of Kerse. Miller's views appear to have been di- 
rected to the navigation of estuaries, and rivers, if not to 
that of the sea itself. Symington, on the present occasion, 
limited himself to the drawing of boats upon a canal. The 
experiment was made upon the Forth and Clyde canal, but 
the boats were drawn at the rate of no more than three 
and a half miles per hour, which did not answer the ex- 
pectations of his patron, and the attempt was abandoned. 
During this attempt, Symington asserts that he was visited 
by Fulton, who stated to him the great value such an inven- 
tion would have in America, and by his account, took full 
and ample notes. In the attempt he thus makes to claim 
for himself the merit of Fulton's subsequent success, he is 
'defeated by the clear and conclusive evidence, that Fulton 
exhibited in a court of law, of his having submitted a plan 
analogous to that he afterwards carried into effect, to Lord 
Stanhope, in 1795, six years prior to the experiment of 
Symington. That Fulton, whose thoughts had continued 
to dwell upon steam navigation, and who saw with pro- 
phetic eye, the vast space for its developement afforded by 
the Mississippi and its branches, should have visited all 
places where steam-boats were to be seen, was natural ; 
but a comparison of the draught of Symington's boat, which 
is still extant, with the boats constructed by Fulton, fur- 
nishes conclusive evidence, that the latter borrowed no 
valuable ideas from the former. 

In the same year, 1801, Evans made, at Philadelphia, an 



286 FULTON. 

experiment of a most remarkable character. Being em- 
ployed by the Corporation of that city to construct a 
dredging machine, he built both the vessel and the engine 
at his works, a mile and a half from the water. The whole, 
weighing 42,000 lbs., was mounted upon wheels, to 
which motion was given by the engine, and thus con- 
veyed to the river. A wheel was then fixed to the stern 
of the vessel, and being again set in motion by the engine, 
she was conveyed to her destined position. Evans, how- 
ever, appears long to have abandoned the hopes of exciting 
his countrymen to enter into his projects of locomotion, 
and content with his steady business as a mill-wright, and 
the proof he had thus given of the soundness of his ancient 
projects, pursued the matter no farther. 

We have thus completed the review of those attempts at 
navigation by steam which were abortive, either from abso- 
lute deficiency, or from their not fulfilling the expectations 
of the parties interested. It is now our more gratifying 
task to record instances of complete success. Livingston, 
who, as we have stated, carried with him to France, a san- 
guine belief that steam navigation was practicable, met 
Fulton at Paris. They were immediately drawn to each 
other by similarity of views, and the latter undertook to 
make those investigations which the avocations of the oth- 
er prevented him from doing. It occurred to Fulton that 
the first step towards success was to investigate fully the 
capabilities of different apparatus for propulsion. These 
preliminary experiments were made at Plombieres, and led 
to the conviction, that of all methods hitherto proposed, 
the paddle-wheel possessed the greatest advantages. He 
next planned a mode of attaching wheels to the engine of 
Watt, ingenious in itself, but complicated, and which he 
afterwards simplified extremely. 

Up to this time, the relation of the force of the engine 



FULTON. 287 

to the velocity of the wheels, and the resistance of the 
water to the motion of the vessel, had never been made a 
matter of preliminary calculation. Aware, however, that 
upon a proper combination of these elements, all positive 
hopes of success must depend, he had recourse to the re- 
corded experiments of the Society of Arts, and limiting his 
proposed speed to four miles per hour, planned his ma- 
chinery and boat in conformity. The experimental vessel 
was then constructed at Paris, and being launched upon 
the Seine, performed its task in exact conformity to his an- 
ticipations. It was then, as afterwards, remarkable, that 
by a sound view of theoretic principles, the single boats of 
Fulton always possessed the speed which he predicted at 
the moment of planning them. This was not the case 
when he attempted double vessels, in consequence of his 
leaving out of view that important resistance which was 
mentioned in speaking of Miller's vessel. 

This preliminary experiment was performed in 1803. 
While Fulton was engaged in preparing for it, a person of 
the name of Des Blancs, who was possessed of a patent for 
apparatus for steam navigation, endeavoured to interrupt it 
as an infringement on his rights. Fulton, however, com- 
municated to him his preliminary experiments, in which he 
had found paddle-wheels superior to the chain of floats 
proposed by Des Blancs, and the opposition ceased. The 
trial on the Seine having proved successful, it was resolved 
to take immediate measures to have a boat of large size 
constructed in the United States, but as at that time the 
work-shops in America were incapable of furnishing a 
steam engine, it became necessary to order one from Watt 
and Bolton. This was done, and Fulton proceeded to 
England to superintend its construction. In the mean- 
time, Livingston was sufficiently fortunate to obtain a re- 
newal of the exclusive grant from the state of New-York. 



288 FULTON — BELL. 

We here remark an anachronism in the work of Stuart. 
Symington's own narrative as given by that author seems 
to place the interview with Fulton in 1801. Stuart in a 
subsequent place refers it to the date of this visit of Ful- 
ton's to England. We have previously stated it as happen- 
ing at the former date upon Symington's authority, as 
this is alone consistent with the expression of astonishment 
that he records. For this could hardly have been uttered 
subsequent to the trial made upon the Seine. Each of the 
dates however, causes a dilemma. If he saw Symington's 
boat in 1801, he returned to France with his previous im- 
pressions in favour of paddle wheels, very much weakened : 
if not until 1804, he had already performed more than 
Symington. 

In like manner the claim of Henry Bell, so pertina- 
ciously maintained by British authors, falls to the ground. 
Bell claims the merit of having furnished Fulton with the 
plan of his successful steam-boat on the ground of his 
having furnished plans and drawings, which he heard two 
years afterwards from Fulton, were likely to answer this 
end. On receiving this letter, he states that " he was led 
to consider the folly of sending his opinions on these 
matters to other countries and not putting them into prac- 
tice in his own." Now as Bell did not build his first boat 
until 1812, we cannot place the date of Fulton's second 
letter, earlier than his return to America, in 1806, and that 
it was written from America, Bell's expressions render 
evident. Fulton therefore could have derived no benefit 
from his advice, for his experiment in France was in 1803, 
and the engine of Watt and Bolton, which was first used 
on the Hudson, must have been ordered at least a year 
before the alleged date of Bell's communications. Neither 
can we reconcile his claims with the statement made by his 
friends, that he was several years in bringing his plans ta 



FULTON — STEVENS. 289 

perfection, and his boat was after all very inferior to those 
constructed by Fulton several years earlier. The anxiety 
of the British public to transfer the honours of Fulton to 
Bell, is manifest from a report of a Committee of Parlia- 
ment, where it is stated that Bell came to this country to 
construct boats for Fulton, while it is now admitted that he 
never was on this side of the Atlantic. We apprehend, 
however, that the correspondence with Bell took place on 
a different occasion. When Fulton planned his ferry 
boats for the East River (New- York), he proposed to make 
them double, he therefore naturally desired to know some- 
thing of Miller's vessel which he had never seen, and by 
Bell's own statement, the request of Fulton for information 
was limited to that single object. Bell asserts that he 
furnished, in addition, views and plans of his own, but long 
before this time Fulton's boats were in successful opera- 
tion, and many competitors had already appeared, not only 
in those places where no exclusive grant existed, but even 
within the waters of the state of New-York. 

The engine ordered from Watt and Bolton reached 
New-York towards the close of the year 1806, and the 
vessel built to receive it was set in motion in the summer 
of 1807. The success that attended it is well known. 

In the mean time Livingston's former associate, the 
elder Stevens, had persevered in his attempts to construct 
steam-boats. In his enterprize he now received the aid of 
his son, and his prospects of success had become so flat- 
tering, that he refused to renew his partnership with 
Livingston, and resolved to trust to his own exertions. 
Fulton's boat, however, was first ready, and secured the 
grant of the exclusive privilege of the State of New-York. 
The Stevens', were but a few days later in moving a 
boat with the required velocity, and as their experiments 
were conducted separately, have an equal right to the 

37 



290 FULTON — STEVENS. 

honours of invention with Fulton. Being shut out of the 
waters of the State of New-York by the monopoly of 
Livingston and Fulton, Stevens conceived the bold design 
of conveying his boat to the Delaware by sea, and this boat, 
which was so near reaping the honour of first success, was 
the first to navigate the ocean by the power of steam. 

From that time until the death of Fulton, the steam-boats 
of the Atlantic coast were gradually improved until their 
speed amounted to eight or nine miles per hour, a velocity 
that Fulton conceived to be the greatest that could be given 
to a steam-boat. To this inference he was probably led by 
the observation of the increased resistance growing out of 
the wave raised in their front. His three earlier boats, 
the Clermont, the Car of Neptune, and the Paragon were 
flat bottomed, their bows forming acute curved wedges, 
the several horizontal sections of which were similar. His 
last boats had keels, but they were introduced for no other 
purpose than to increase their strength. In the boats con- 
structed by his successors, after his death, a nearer approach 
was made to the usual figure of a ship, but the waves still 
formed an important obstacle. In the mean time the 
younger Stevens was steadily engaged in improving steam 
navigation, each successive boat constructed under his 
direction possessing better properties than the former. 
The view he took of the subject was different from that 
of Fulton, believing that the great size of the wave was 
owing to defective form, he instituted experiments, both on 
alarge and small scale, to determine the figure in which this 
obstacle is of least magnitude. On the setting aside of the 
exclusive grant of the State of New-York to Livingston 
and Fulton, he prepared a boat for navigation of the 
Hudson, which performed its voyages at the rate of 
13 and a half English miles per hour. In the various 



y 



STEAM NAVIGATION. 291 

attempts which spirited competition has brought forward, 
this velocity has not yet been exceeded. 

Steam-boats were not introduced into Great Britain 
until 1812, five years later than the successful voyage of 
Fulton. Bell, whose name has already been mentioned, 
built the first upon the river Clyde at Glasgow. In March, 
1816, the first steam-boat crossed the British Channel from 
Brighton to Havre. Since that period their use has been 
much extended, and their structure improved, but no 
European steam-boat, has as far as we can learn attained a 
speed of more than 9 miles per hour. 

In 1815, steam-boats, previously constructed by Fulton 
for the purpose, commenced to run as packets between 
New- York and Providence Rhode-Island, a part of which 
passage is performed in the open sea. One of these 
vessels had been intended to make a voyage to Russia, 
but the greatness of the expense deterred the proprietors 
from undertaking it. This voyage was performed in 1817, 
by the Savannah, and in 1818, a steam-ship plied from New- 
York to New-Orleans as a packet, touching at Charleston 
and the Havana. 

In 1815 also, a steam-boat made a passage from Glas- 
gow to London, under the direction of Mr. George Dodd, 
but it was not until 1820 that steam-packets were esta- 
blished, between Holyhead and Dublin. In 1825, a passage 
was made, by the steam -ship Enterprize, from London to 
Calcutta. All doubts, therefore, in respect to the practica- 
bility of navigating the ocean by steam may be considered 
as settled. In point of economy, however, it can never 
compete with sails, and hence probably can only be used 
to advantage for conveying passengers, or for purposes of 
war. 

In the steam-boats of the Ohio and Mississippi, high 
pressure engines are now in the most general use. The 



292 STEAM CARRIAGES. 

boilers are usually cylindrical, with internal flues, and the 
favourite position of the cylinder is horizontal, resembling 
the engine on PI. IV. Many of them, however, have 
conical valves, which are necessarily placed in vertical 
boxes, this has demanded a novel arrangement of the steam 
and eduction pipes, and of the apparatus for working the 
valves. An engine of this description has recently been 
placed in a boat upon the Hudson River, but was not 
finished in time to obtain a draught of it for this work. 
The boiler is to be tubular, and the furnace to have a 
peculiar structure for burning anthracite coal. Great 
expectations are entertained of the performance of this 
vessel. 

In France Steam Navigation has been of even more re- 
cent introduction than in England. Five years, as we have 
seen, elapsed from the time of Fulton's successful voyage 
until Bell navigated the Clyde, four more passed before a 
boat, built in England, crossed the Channel, and proceeded 
up the Seine to Paris. We have given, in the form of 
Appendices, lists of all the French and English steam- 
boats, that we could ascertain to have been in use at the 
close of the year 1827. A similar hst was prepared, as far 
as materials could be obtained of American steam-boats. 
It was, however, far from perfect, and being informed that a 
list is now preparing by authority, it has been considered 
best to cancel that which had been prepared, and publish 
the official record as a supplement. 

As steam navigation took its rise on the Hudson, so the 
steam-boats, navigating that river, have uniformly been 
before all others in point of speed ; and those constructed 
under the direction of Mr. R. L. Stevens, have held the 
first place among those of the Hudson. Two of his ves- 
sels have an average speed of 13i miles per hour, and this 
has on occasions of competition been exceeded. Others 



STEAM CARRIAGES. 293 

have approached this same speed so nearly, that the differ- 
ence of passage has not been many minutes in the distance 
of nearly 150 miles. In a passage recently made by the 
author, on the Hudson, the wheels of the New-Philadelphia 
averaged 25i revolutions per minute, and the piston moved 
with a velocity of 405 feet per second, being 21 feet more 
than has been stated on a former page as the velocity of 
those of the North- America. In this increase of speed 
and consequent expenditure of fuel, no very important ad- 
vantage seems to have been gained, except the distancing 
of competitors, the relative velocity of the wheels being 
far more increased than that of the boat. 

203. Steam is also employed to move carriages upon the 
land. For this purpose, the wheels of the carriage are set 
in motion by the engine, in the same manner that the pad- 
dle-wheels of a steam-boat are caused to turn ; the friction 
which they experience upon their track causes them to 
move forward, unless they meet a resistance to their pro- 
gressive motion equal to this friction. The experiments of 
Coulomb and Vince show, that, under the circumstances in 
which wheels act, the friction of their circumference will 
depend upon the weight with which they are loaded, and 
the nature of the rubbing surface, but not in the least upon 
the velocity. The tire of wheels is made of iron, and 
steam-carriages usually run upon tracks, also of iron, form- 
ing what is styled a rail road. Rail roads are parallel bars 
of iron, laid either level, or with a gentle and uniform 
slope, and steam has, as yet, only been usefully applied to 
locomotion, upon roads of this character. The reasons 
why they should be superior in this respect to a common 
road are obvious. The resistance is not only regular and 
uniform, but equal upon every wheel, while on a common 
road, there is a constant variation in slope, and in the na- 



294 STEAM CARRIAGES. 

ture of the surface, and besides, obstacles are frequently 
met that affect but one of the wheels, and thus tend to turn 
the carriage to one side. In spite of these difficulties, some 
tolerably successful experiments have been performed with 
steam-carriages upon common roads. 

The case, however, that is most usual, is motion upon 
rail roads. Here the friction is that of iron against iron. 
We cannot anticipate that the wheels will be prevent- 
ed from sliding upon a rail road by the maximum fric- 
tion that takes place between two pieces of iron in experi- 
ments ; dust, moisture, and other circumstances, interfere 
to lessen the adhesion. It cannot, therefore, be safely ta- 
ken at more than -^^ the part of the weight. If there be a 
force applied, sufficient to cause the wheels of a carriage 
to turn around, it will continue to go forward until the 
resistance become equal to g^^th the weight of the carriage. 
The carriage is,"therefor6, under the same circumstances, 
as if it were drawn forward by a cord, capable of bearing 
a strain of ^^ih. part of its weight. 

The resistances to the progressive motion, are the friction 
upon the axles of the wheels, and the disturbances growing 
out of lateral shocks. The friction of steel axles upon brass 
boxes, well coated with oil, is ^^th the part of the weight, 
and the force applied to overcome it, has its intensity in- 
creased, in the ratio of the radius of the crank to the ra- 
dius of the axle. As the radius of the crank of a given 
power cannot be increased, without diminishing the area of 
the piston, or its own velocity, there is no gain by simply 
varying the proportions of its engine. On the other hand, as 
with an equal number of revolutions, points will move faster 
on the circumference of a larger wheel, than they will on 
a smaller one, and the progressive motion will depend on 
the velocity of the circumference, there is a constant and 
regular gain in velocity, by increasing the diameter of the 



STEAM CARRIAGES. 295 

wheels. This, however, has its limit in practice, for by 
increasing the diameter of the wheels, the centre of gravity- 
is raised, and the machine becomes unstable. 

It might, at first sight, appear that, as the friction which 
causes the carriage to go forward increases with its weight, 
heavy carriages and engines were the best for locomotion, 
but the resistances increase also with the weight, and thus 
all weights not absolutely essential to the structure of the 
engine are disadvantageous. Hence, for locomotion, no 
other engine but that of high pressure can be admitted, for 
condensing engines of equal power, are not only heavier in 
themselves, but require a quantity of cold water for con- 
densation, that would, of itself, furnish a load for the en- 
gine. So'also the boiler, and the load of water should be 
the smallest, that is consistent with the generation of the 
necessary quantity of steam. 

The workmanship of the carriages used on rail-ways, has 
been regularly improving for several years past, and is pro- 
bably still far from perfection ; we, therefore, cannot state 
any proportion between the weight that can be drawn upon 
a rail road, by a locomotive steam engine, and the weight 
of itself and the carriage that bears it, that would be cer- 
tainly true a few months hence. The latest calculations 
seem to admit, that a locomotive carriage will drag after it, 
in carriages furnished with wheels equal in diameter to its 
own, at least seven times its own weight. Neither do we 
venture to give any proportion between the actual resis- 
tance and the weight, by which the propelling power may 
be calculated. At the present moment, too, friction-sav- 
ing apparatus is eagerly sought for, and made the subject 
of experiment, by which the friction still remaining, after 
the materials and workmanship have reached the greatest 
perfection practicable, may probably be reduced many fold. 



296 STEAM CARRIAGES. 

Borne few principles useful in practice may, however, be 
stated. 

Friction opposes a resistance which has a constant mea- 
sure at all velocities, but the measure of the power requir- 
ed to overcome it, will depend both on the resistance and 
the velocity. Hence the powers of engines, by which dif- 
ferent velocities are obtained in the same carriage, are pro- 
portioned to the velocities. But as the time for passing 
over a given space is inversely as the velocity with which 
the distance is performed, a given distance will be perform- 
ed at any velocity whatever, with a constant expenditure of 
fuel. 

If the same locomotive engine have its velocity increased 
by lessening the load it drags, or diminishing the friction, 
by both of which methods a limited change in velocity may 
be attained, the expenditure of steam will then be inversely 
as the velocities. 

It is, therefore, obvious, that when speed is the sole object 
in view, locomotion on land soon becomes more advanta- 
geous than steam navigation, for the power in the latter 
case increases as the cubes of the velocities ; and the 
expenditures of fuel as the square. On the other hand, 
friction on rail roads has not yet been so much diminished 
as to enable them to compete, either with steam or canal 
navigation, in the conveyance of heavy loads, at small 
velocities. The friends of rail roads, however, anticipate 
that they will soon be enabled to lessen the friction so 
much as to place them, in all respects, on a par with 
either of the other species of transportation. There is 
in truth, friction-saving machinery, such for instance as 
the apparatus of Atwood, and the patent block of Garnett, 
which act so well as to give fair ground to such anticipa- 
tions ; whether the same beneficial result can be obtained 
in the wheels of carriages, remains to be shewn by experi- 
ment. 



STEAM CARRIAGES. 297 

204. Evans, as Has been already mentioned, was the 
first who entertained rational hopes of being able to move 
carriages by steam, for we must reject the views of Robi- 
son and Watt as wholly impracticable ; and indeed the 
impossibility of using the condensing engine was ascertained 
and admitted by Watt. Evans not only was the first to 
entertain correct views, but was also the first to submit 
them to practice, in the removal of his dredging machine, 
which has been before referred to in the present chapter. 

In 1802, Trevithick and Vivian took out a patent for the 
application of their engine to propel carriages upon rail- 
roads. In 1804, they published a description of a carriage 
intended for common roads, but it was not until 1806, that 
an actual experiment was made. This was performed 
upon the Merthyr Tydvil Rail-Road, in Wales. The 
performance of the ^apparatus was, however, far less than 
might have been anticipated from its power, and this was 
ascribed to a want of sufficient adhesion of the wheels to 
the rails. We recollect having heard this failure ascribed 
to the circumstance that but one of the wheels was set in 
motion by the engine ; but all the authorities that we 
have consulted seem to agree, that all the four wheels 
were made to revolve. 

The failure, which, had the first statement been true, 
is at once to be accounted for, becomes difficult to explain 
if these authorities state the real circumstances. 

A difficulty, however, in the use did occur, and being 
ascribed to the cause that has been mentioned, a person 
of the name of Blenkinsop undertook to obviate it. For 
this purpose he laid a rack, or rail cut into teeth, between 
the other two rails, along the whole extent of road ; into 
this a pinion, set in motion by the engine, caught. This 
method was found effectual at slow velocities, and was used 
from the year 1801, in which it was invented, nearly up to 

38 



298 STEAM CARRIAGES. 

the present time, at Middleton Colliery, near Leeds in Eng- 
land. It will not admit of great velocities, but is applicable 
to the rising of ascents far more steep than can be over- 
come by the mere adhesion of the wheels to the road. 

In 1812, Messrs. W. & E. Chapman obtained a patent 
in England for a locomotive engine, the power of which 
was applied by means of a chain fixed at the two ends, 
and passing over an axle upon the carriage that was caused 
to revolve by the engine. 

In 1813, Mr. Brunton, of Batterly Iron Works, proposed 
a plan for locomotion by steam, in which he employed a 
system of levers, resembling, in their action, the bones of 
the human leg. 

In 1815, Dodd and Stephenson, of Killingworth, in 
England, returned to the original principle of adhesion, 
and were completely successful, shewing that on rail-roads, 
absolutely or nearly level, the friction was sufficient to 
produce progressive motion, in all cases except when the 
rails were covered with snow. Their engine had six 
wheels, two of which were moved by the engine, and the 
others connected with them by an endless chain passing 
over drums. No advantage, however, is gained by the use 
of more than four wheels, and any additional number has 
since been laid aside. 

Locomotive engines have received since that time, con- 
tinual improvements. Two cylinders have been used each 
acting upon a pair of wheels. The next step was to use 
two cylinders acting at right angles to each other upon the 
same pair of wheels, and to move the others by connecting 
rods. Such is the very beautiful mechanism delineated on 
PI. IX. which was made under the direction of Mr. Hora- 
tio Allen for the Delaware and Hudson Rail-Road Co. at 
Stourbridge, in England. 



STEAM CARRIAGES. 



299 



In these several improvements, the weight of the engine 
and its parts were gradually increased to an excessive 
amount. The centre of gravity was also raised so high as 
to render the carriages unstable. In consequence of this, 
a search has more recently taken place for engines and 
carriages of small weight. This has been successful in a 
remarkable degree, in locomotive engines exhibited upon 
the Manchester and Liverpool Rail-Roads. The details of 
these experiments are to be found, in the Mechanics' 
Magazine for November and December, 1829, and in the 
Quarterly Review for March, 1830, to which we refer our 
readers. A draught of the most remarkable of these 
engines, "the Novelty," is subjoined. 




A locomotive engine, that promises to perform as well 
as the Novelty, with a boiler of novel construction for 
burning anthracite coal, has been recently exhibited in 
New-York. It is the invention of Col. Miller of Charles- 
ton S. C, and is intended for the great rail-road now con- 
structing in that State. 



205. In concluding this work a few reflections on the 
importance of the subject may not be irrelevant. The 
steam engine has been described in its most usual and most 
perfect forms ; in the historical sketch it has been traced 
fi^omthe earliest notices of the knowledge of the mechani- 



300 CONCLUSION. 

cal power of steam, down to the present important space 
that it has occupied. Feeble and imperfect in its first 
beginnings, and limited for nearly a century after its intro- 
duction to a single, and by no means important object, it 
became in the hands of Watt an instrument of universal 
application. It is now equally subservient to those purpo- 
ses which require the greatest delicacy of manipulation, 
and those which demand the most intense exertions of 
power. Its introduction and gradual improvement have 
required inventive talents of the highest order, and the 
exertions of genius the most sublime ; in its uses we see 
developed and realized, not only the brilliant conceptions 
of poetry, but the wildest fables of romance ; it has 
already changed the state of the world, and altered the 
relations of civilized society ; and in its farther progress it 
seems to promise to perform even more important services, 
and to fulfil yet higher destinies. 



APPENDIX, No. I. 



ON THE TENSION OF AQUEOUS VAPOUR, 

BY MESSRS. ARAGO & DULONG. 

In order that the French Academy of Sciences might reply 
to the questions made by the government, it became necessary 
to determine the elastic force of vapour at the highest tempera- 
tures. A labour of an entirely new description was to be un- 
dertaken, not only of the greatest value to science, but to man- 
ufacturing industry. This labour demanded a skill in manipula- 
tion rare even among the most skilful professors of physical 
science, as well as the most profound knowledge of the subject. 
In addition, it exposed the experimenters to dangers, against 
which there was no security that was absolutely certain. It 
has been performed by Messrs. Dulong and Arago, and its pub- 
lication will form an important era in science. 

Extracts from the Minutes of the Academy of Sciences, for 
Monday, SOth November^ 1829. 

M. Dulong, on behalf of a committee composed of Messrs. 
Arago, Prony, Ampere, Girard, and himself, made a report en- 
titled, " Account of experiments made by order of the Academy 
of Sciences, to determine the elastic force of aqueous vapour at 
high temperatures.^^ 

The law which fixes the precautionary measures, to which 
the construction of steam engines is to be subjected, prescribes, 
among others, the use of valves of metal, fusible at tempera- 
tures that exceed by from 10° to 30° (Centigrade) the temper a^ 



302 APPENDIX NO. I. 

tuTes that correspond to the elasticity of the vapour employed in 
the habitual work of the machine. 

The execution of this condition requires, as may be easily 
seen, that the temperature, corresponding to a given elasticity, 
should be known. This was a desideratum in science, and 
the committee of which M. Dulong is the organ, was charged 
with the duty of supplying this want. M. Dulong was espe- 
cially entrusted with the construction of the apparatus, and with 
the direction of the experiments. M. Arago also co-operated 
in the labours of his colleague ; and made in conjunction with 
him a great number of experiments. 

The committee, desirous of giving its labours all the perfection 
adapted to, and demanded by the present state of science, and be- 
sides presuming that it would be long before another opportunity 
would occur of beginning and completing observations of the 
same description, rejected, as inexact, the process whichc onsists 
in estimating the elastic force of vapour by means of a safety 
valve loaded with a weight, and resolved, in spite of the difficulty 
{ittending such an undertaking, to have recourse to the direct 
Pleasure of the column of Mercury, which would be kept in equi- 
Jibrio by the elasticity of the vapour. 

When this elasticity does not exceed a small number of atmos- 
pheres, the direct measure of this column does not present any 
difficulty ; but, as in this case, the value of pressures of from 20 
to 30 atmospheres were to be ascertained, it became necessary to 
enclose a column of mercury, of 70 or 80 feet in height, in a tube. 
This tube must be of glass, in order that the height of the mercu- 
ry might be readily observed in all positions. It may be easily 
seen with what difficulties the execution of such a project must 
be attended. 

However, all these difficulties were surmounted, and the appa- 
ratus erected, in the ancient square tour known by the name of 
Tour de Clovis, the only remains of the ancient church of St.. 
Genevieve. 

The apparatus might have been reduced to but two essential 
parts : a boiler, intended to furnish the steam, and a glass tube 



APPENDIX NO. I. 303 

employed to support the mercurial column ; but it was to be 
feared that too rapid an augmentation of the tension of the va- 
pour, followed by the opening of the safety valve, might give rise 
to an action like that which takes place in the hydraulic ram ; this 
would have endangered the more brittle parts, and given rise, in 
consequence, to the loss of a great quantity of mercury. Pru- 
dence required that this accident should be guarded against. 

In order to obviate it, it was resolved not to place the columiti 
of mercury in contact with the steam ; but to make use of an in- 
termediate instrument, a species of guage, which should give 
with exactitude the same indications as the column of mercury, 
without being liable to the same inconveniences. 

The operations relating to the measure of the tension of the 
steam, were, in consequence, preceded by a preliminary opera- 
tion, which consisted in ascertaining exactly the degree of elas- 
ticity that a known mass of air would assume, when its volume 
was diminished in a given proportion. A known mass of air was 
in consequence subjected to pressures increasing gradually from 
one to twenty atmospheres. The volume corresponding to each 
of these pressures was carefully noted, and henceforth this mass 
of air might be substituted for the troublesome column of mer- 
cury, and the different volumes the air assumed, would furnish, 
with the greatest accuracy, measures of known weight. 

This preliminary operation, which, in consequence of local 
circumstances, became at length of absolute necessity, also fur- 
nished the means of exactly verifying one of the most useful 
laws in Natural Philosophy, namely, that which is known by 
the name of Mariotte. 

This law, which had been verified within certain limits, was 
far from being established in a satisfactory manner at high pres- 
sures. The late observations of Dulong and Arago, no longer 
leave any doubt in this respect. A table drawn up by these com- 
missioners themselves, gives the results of thirty- nine experi- 
ments, made on the same air, submitted to pressures varying 
between one and twenty-seven atmospheres, within which the 
aw of Mariotte is never at fault an appreciable quantity. 



304 APPENDIX NO. I. 

The Committee of the Academy naturally desired to subject to 
observation, by means of the apparatus, two or three other spe- 
cies of elastic fluids, and ascertain whether they also followed 
thelaw of Mariotte; but it was considered proper first to com- 
plete the researches demanded by the government; and when 
these researches were terminated, it was impossible to obtain 
from the administration of buildings, the use of the place where 
their apparatus was set up. This circumstance, says M. Dulong, 
is so much the more vexatious, inasmuch as we might have com- 
pleted the illustration of this important point of the Mechanics of 
gases, without any additional expense, and in a very short space 
of time; which it would now require a considerable expense and 
several months of labour, to take up this subject a second time 
at the point where we left it. 

The Committee obtained, as we have seen, a guage by aid of 
which they could ascertain the tension of vapour, with an exact- 
ness equal to that which is attainable by direct experiments with 
a column of Mercury. It was sufficient to make a boiler commu- 
nicate with the reservoir of this guage, in order to complete the 
resolution of the problem. In following this course they ob- 
tained the great advantage of avoiding the inconveniences that 
have already been pointed out, and which consist in the oscilla- 
tions of the mercurial column. 

The apparatus was disposed in such a manner that a steam 
boiler could be substituted for the forcing pump, without derang- 
ing any other part. But fearing the effects of an expolsion in a 
ruinous tower, and particularly in consequence of its vicinity to 
the College of Henry IV., the Committee resolved to transfer, 
with every precaution, the apparatus completely set up, to the 
courts of the Observatory. 

The exact measure of elevated temperatures of steam, de- 
mands precautions, the neglect of which has led some observers 
into considerable errors. 

The first precaution consists in keeping an account of the cool- 
ing produced by the atmospheric air, in the part of the boiler 
which is placed outside of the brick work. This can only be 



APPENDIX NO. I. 305 

determined with accuracy, by keeping the whole of them at a 
constant temperature, and this was carefully attended to. 

The second consists in not exposing the thermometer that 
serves to measure the temperature, to the direct pressure of the 
vapour, particularly when this pressure is great. For even if a 
thermometer could be found capable of bearing the pressure 
without breaking, it would sustain a pressure that would tend to 
raise the column of mercury, independently of the temperature, 
and would thus produce a cause of error, of which it would be 
difficult to keep an account. In order to obviate this difficulty, 
which has not been previously perceived by any experimenter, it 
was contrived that the thermometers should be placed in tubes 
closed at one end, and filled with mercury. These tubes were 
chosen very thin, in order to oppose as little delay as possible to 
the transmission of heat, and they were filled with mercury. 
One of these thermometers was plunged to the bottom of the 
boiler, and gave the temperature of the liquid water ; the other, 
of less length, reached only to within a few inches of the surface 
of the water, and gave the temperature of the vapour. 

Our information, in respect to the elastic force of vapour, was, 
as we have stated, almost nothing at the epoch when the commis- 
sion commenced its labours. At a tension beyond eight atmos- 
pheres, we only possess a single number, communicated to Mr. 
Clement by Mr. Perkins ; but this number (215°) has been found 
wholly erroneous. The force of the vapour was given at 35 
atmospheres, while, in truth, it is no more than 20. (Vapour, 
in order to balance 35 atmospheres, should have a temperature 
of 245°.)* 

Germany was farther advanced than England. M. Arzberges, 
Professor in the Polytechnic Institution of Vienna, had made 
experiments upon the temperature of vapour, which he had ex- 
tended as far as twenty atmospheres. He had employed, in 
order to determine the elasticity of the vapour, safety valves 

* It appears that the French Committee were unacquainted with the 
experiments of Taylor, which extend to 16 atmospheres. 

39 



306 APPENDIX NO. I. 

with levers, a method defective in itself, but of which he had 
corrected the errors by very ingenious precautions. (The 
most remarkable of these, consisted in employing a spherical 
valve of steel, resting on the circumference of an aperture made 
in a piece of the same substance.) 

The numbers which he obtained are not, however, exact, and 
the defect arises out of his having neglected, in raising the tem- 
perature, the two indispensable precautions that have already 
been pointed out, that of withdrawing the thermometer placed 
within the boiler from the direct pressure of the steam, and 
that of taking into account the cooling produced by a part of 
the stem of the thermometer, being exposed to the air. 

The errors which arise from these two omissions, affect, it is 
true, the results in opposite ways ; but their effects do not com- 
pletely counteract each other at high temperatures. The second 
exceeds the first, and would cause the temperatures to be esti- 
mated above what they really were. Thus M. Arzberges found 
that the pressure of 20 atmospheres corresponded to a tempe- 
rature of 222° Cent, while it is in truth attained at a tempera- 
ture of 215° Cent. 

The law which would express the elastic force of the vapour 
in terms of the temperature, is not known, and does not ex- 
hibit itself more clearly in the new observationsof our academi- 
cians, than it did in those they already possessed, in the lower 
part of the thermometric scale. In the mean time, a formula 
of interpolation has been s aught, arl&ing from expeiiment alone, 
and fitted to make known the elastic force at any point of the 
ihermometric scale. 

A great number of formulae fitted to attain this object, had 
Ijeen proposed to the Committee by different authors. No one 
of these formula has borne the proof when applied to high tem- 
peratures. A single remarkable exception must be made. M. 
Roche, Professor at Strasbourg, setting out, not from experi- 
ment, but from theoretic views of his own, had arrived at re- 
sults which are conformable, in a remarkable degree, with those 
obtained at the Observatory. 



APPENDIX NO. I. 307 

The opinions of M. Roche, are, if we mistake not, submitted 
to the judgment of the Academy of Sciences, which is about to 
report upon them. 

The formula of interpolation, on which the Committee have 
rested, is as follows : 

e=(lx0.7153 5. 
e is the elasticity, t the temperature, and the pressure of a sin- 
gle atmosphere is taken as the unit. 

This formula represents all the experimental results with 
great accuracy, up to 24 atmospheres. 

The greatest error to which its application gives rise, is at 
eight atmospheres ; it is then nine-tenths of a centigrade de- 
gree. 

As to the temperatures corresponding to pressures beyond 
24 atmospheres, the preceding formula gives them with so much 
the more ease, inasmuch as it has been calculated from the 
highest of the observed pressures. The confidence with which 
it inspires the Committee is such, that they are convinced that 
at 50 atmospheres, the error would not exceed one-tenth of a 
degree (Centigrade.) 

The temperatures for pressures greater than 24 atmospheres^ 
have been calculated up to 100 atmospheres, but only for every 
five degrees. 

We give beneath the numbers, extracted from an account of 
them presented to the Academy. 



308 



APPENDIX NO. I. 



Table of the elastic force of Aqueous Vapour, corresponding to 
Pressures of from 1 ^o 24 Atmospheres, from experiment, 
and from 2^ to 50 Atmospheres, by calculation. 



Elasticity of 
Vapour in At- 
mospheres. 


Corresponding Tennpera- 
tures in degrees of the 
Cpntisrade Thermometer. 


Elasticity of 
Vapour in At- 
mospheres. 


1 

Corresponding Tempera- 
tures in degrees of the 
Centigrade Thermometer. 


1 


100'' 


13 


193.7 


n 


112.2 


14 


197.19 


2^ 


121.4 


15 


200.48 


2i 


128.8 


16 


203.6 


3 


135.1 


17 


206.57 


3i 


140.6 


18 


209.4 


4 


145.4 


19 


212.1 


4i 


149.6 


20 


214.7 


5 


153.8 


21 


217.2 • 


51 


156.8 


22 


219.6 


6 


160.2 


23 


221.9 


6i 


163.48 


24 


224.2 


7 


166.5 


25 


226.3 


8 


172.1 


30 


236.2 


9 


177.1 


35 


244.85 


10 


181.6 


40 


252.55 


11 


186.03 


45 


259.52 


12 

u 


190.00 


50 


265.89 

. — f 



Note. — [These results are entirely different from those given 
on page 34, and from those of all former experimenters. We have 
given them as emanating from the highest and latest authority, 
but we cannot help feeling some hesitation in receiving them in 
opposition to the authorities of Dalton, Robinson, Ure, and 
Watt.] 



APPENDIX No. 11. 



ON THE EXPLOSIONS OF STEAM ENGINES. 

BY M. ARAGO. 

Steam Engine^ may be considered as the highest efforts of 
human industry, so soon as it shall be possible, either to render 
the explosions, that at present sometimes affect them, impossi- 
ble, or at least to prevent, by sure methods, these accidents from 
causing the scenes of destruction and death that too often attend 
them. It must be confessed that this problem has not been 
hitherto completely solved, although it has excited the attention 
of men of science and of the most intelligent artists. The in- 
genious mechanism of Papin known under the name of the 
safety valve, suffices it is true in ordinary cases; but there are 
others, although they are happily rare, in which it is not 
only insufficient but even dangerous. To examine these cases, 
as far at least, as the imperfect state of our knowlodge will 
permit, to point out their causes, and some means, more or less 
plausible to avoid them, such is the object of this chapter. 

I shall first lay before my readers an abridged relation of all 
the explosions which are known to me, and which have had as 
their witnesses or historians, experienced engineers. It is in 
such a narration that we shall find the means of appreciating 
the different explanations that have been given of these terrify- 
ing phenomena. 



310 APPENDIX NO. II. 

Instances of the greatest effects that explosions have hitherto 

produced. 

Lochrin is the name of an immense distillery situated near 
Edinburgh. The proprietor in search of economy, resolved 
some years since, to substitute, for the ancient mode of distilla- 
tion, that in which steam is employed. For this purpose large 
metallic tubes in which a current of vapour constantly circula- 
ted, traversed from side to side, the vessels containing liquids 
that were to be boiled. The vapour that heated them was 
generated in a boiler of wrought iron, more than a third of an 
inch in thickness, thirty-seven feet in length, three feet wide at 
bottom, two feet at the spring of the cover, and four feet in 
depth. The whole weight of the boiler was nine tons. On its 
top were two safety valves, so disposed as to open as soon as 
the interior pressure became greater than sixty lbs. per square 
inch. In order that the workmen might iiot overload the safety 
valves, one of them was contained in a cage kept constantly 
locked. 

The immense establishment commenced work on the 21st 
of March, 1814. Twelve days after, it no longer existed, an 
explosion had wholly ruined it. 

At the inststnt of the catastrophe, the boiler divided itself into 
two distinct and unequal portions. The upper portion com- 
posed of the cover and two sides, weighed seven tons. It was 
projected upwards with such force, that, after having traversed 
the brick vault that covered the workshop, and the roof, it rose 
in the air to the height of seventy feet. This enormous mass 
fell one hundred and fifty feet from its original position upon 
one of the buildings of the distillery, crushed it, and finished 
its career by crushing to pieces a great vessel of cast-iron, situa- 
ted on the ground floor. 

Luckily there were but two workmen near the apparatus at 
the moment of the explosion. These were the only persons who 
lost their lives, a circumstance the more extraordinary, as the 
other parts of the works were then full of people, and the 



APPENDIX NO. II. 311 

boiler, like an immense mine, threw in every direction, with 
prodigious velocity, an immense quantity of tools and fwLg- 
ments. The body of one of these workmen was divided in two; 
and it was considered as a fact worthy of notice, that the legs 
remained within the distillery, while the bust was found at a 
distance, among the fragments without the distillery. 

The line along which the boiler was rent, was perfectly hori- 
zontal, and followed a row of bolts as regularly as if the iron 
had been cut with shears. 

The form of the boiler was that adopted by Watt. It was 
concave outwards, in the part of its surface nearest to the fire, 
where it formed a species of arch that permitted the flame of the 
furnace to penetrate to the centre of the liquid mass. After the 
explosion this part of the vessel was found to be convex, so 
powerfully had it been pressed outwards. This change of 
shape presented nothing that could not readily be explained ; 
but it appeared hardly credible, if an examination of the place 
had not furnished positive evidence, that the bottom of the 
boiler weighing two tons, and showing such evident proofs of 
having sustained an enormous pressure downwards, had not- 
withstanding been raised by the explosion to a height of 14 or 
15 feet, and been carried to some distance from the mass of 
masonry on which it had at first been built. 

It is important to remark, that there was no circumstance 
that would authorize the opinion, that the accident at Lochrin 
arose from a bad construction of the safety valves. I have 
already said that one of them was locked up : we must there- 
fore in like manner reject all idea of an overload. 

. Second instance characterized hy the simultaneous explosion of 

several boilers. 

The Steam-boat Rhone, built by Messrs. Aitken and Steel 
was intended to act as a tow-boat between Aries and Lyons. 
It carried an immense machine, perfectly well executed at 
Paris, in the workshops of La Gare, and was supplied with 



319 APPENDIX NO. II* 

steam by four boilers of iron plate, each 1. 3 meters* in diame- 
ter. Since the explosion it was ascertained that the plate in 
several places was not more than 6 millimetersf in thickness. 

On the fourth of March 1827, while preparing for an experi- 
ment, at which all the magistrates of the city of Lyons were 
to be present, an explosion took place. Many persons, and 
among the rest Mr. Steel, fell victims to this accident. Even 
some of the spectators, on the Quay of the Rhone, were killed 
by fragments of the timber of the boat. The whole deck was 
projected to a vast distance. The flues and chimnies weigh- 
ing more than 30 cwt. rose almost vertically to a considerable 
height. The vault of one of the boilers, fell at a distance of 
more than 800 feet, although it weighed at least a ton. 

This horrible catastrophe was the inevitable consequence of 
the imprudence of the engineer. Vexed at not being able to 
overcome the rapidity of the current, as completely as he had 
hoped, Mr. Steel fastened down the safety valves of all the four 
boilers. This fact, however increditable it may appear, has 
been proved in the most incontestible manner. 

We have remarked, that there were four boilers in the boat. 
It is certain that two of them burst almost simultaneously. If 
I am well informed, it was found on drawing the third of the 
boilers from the Rhone, into which it had fallen, that it had 
burst also. This rupture in the same second of three different 
boilers, is a very singular fact, which we shall have to take into 
account, when we speak of the explanations that have been 
given of these phenomena. 

We must not forget to state, that at Lyons, as at Lochrin, the 
vault, which the explosion threw to the distance of more than 
800 feet, was separated from the rest of the boiler by a rent 
nearly horizontal, although the metal had inequalities in thick- 
ness, along this line, of more than a twelfth of an inch. Mr. 
Tabareau, from whom I obtained these precious details, has 
calculated that this difference in thickness would have given the 

* 4 feet 4J inches. t About a quarter of an inch. 



APPENDIX NO. II. 313 

thicker portions of the vessel an excess of strength of more 
than six atmospheres, out of twenty or twenty-five, which was 
their whole cohesive force. Thus there was a simultaneously 
rupture, in portions of the boiler whose tenacities differed from 
each other, at least six atmospheres. 

I have just remarked, that the simultaneous explosion of 
several boilers, placed upon different furnaces, was a fact worthy 
of attention. It may therefore be useful to cite a second ex- 
ample. 

At the entrance of the tin mine of Polgooth, there is an im- 
mense steam engine supplied by three separate boilers. This 
machine having been stopped for a few moments, in order to 
allow the engineer time to repair the forcing pump that drained 
the mine, two of the boilers burst, one immediately after the 
other. Captain Reed, who was at the moment near the mine, 
reports that the first explosion had hardly ceased when the 
second took place. 

Explosions occasioned hy overloading the safety valve. 

After the explosion, which completely destroyed the Sugar- 
refinery in Wellclose Square, London, it was ascertained that 
the cast-iron of which the boiler was formed, was not suffi- 
ciently thick throughout. At bottom it was found not less than 
two and a half inches in thickness ; on the two sides an inch 
and a half, in the lower part of the dome not more than seven 
sixteenths of an inch, and in some other places, the thickness 
was reduced to an eight of an inch. 

Some seconds before the accident, an agent of the maker, 
vexed at the feeble action of the engine, had, in spite of the 
remonstrances of the refiners, charged the safety valve with an 
enormous weight, while he, at the same time, pushed the fire as 
much as possible. 

It was remarked that at London as well as at Lyons, the 
boiler broke at the same moment, in parts that had such unequal 
thicknesses, that it might be supposed, that the thickest part 
would have required ten times the force to break it, that would 
have sufficed to rend the thinnest. 

40 

1^ 



314 APPENDIX NO. II. 

During the examination instituted by the House of Com- 
mons on the occasion of the explosion of a steam-boat at 
Norwich, Mr. William Chapman, a civil Engineer of Newcas- 
tle, cited the explosion of a boiler, which, like the preceding, 
was caused by overloading the safety valve ; but on this occa- 
sion at least, the self-love of the maker, had no concern in the 
catastrophe ; for it was occasioned by a workmen who seated 
himself on the safety valve, in order to give his comrades the 
spectacle of the oscillating motion, that he would undergo, as he 
said, so soon as the vapour should become strong enough to 
lift him. Thus it happened as may easily be imagined, that 
the valve did not open, but the boiler burst. The fragments 
killed and wounded a great number of persons. 

In America, a steam-boat on the Ohio was blown up, while 
the crew were engaged in weighing anchor ; that is to say, at a 
moment when the machine was not in motion, and there was no 
consumption of steam, although the fire had already attained 
its full force. 

To raise or unload the safety valve is the means of avoiding 
accidents in this case ; but by an inexplicable inadvertency, the 
engineer on the contrary loaded it with an additional weight. 

Explosions preceded by a great weakening in the tension of the 

vapour. 

In all the cases of explosion, hitherto cited, (that of Lochrin 
excepted) it has been stated, that the safety valve was either 
wholly shut, or loaded with too great a weight. The cause of 
the giving way of the boiler therefore seems evident. We are 
now about to enter into the examination of a series of facts 
far less simple. Several of them, indeed, I frankly avow have a 
paradoxical appearance, which at first sight inspires doubt. But 
the instances are numerous, and the authorities unquestionable. 

Some seconds before the cast-iron boiler, containing steam 
of a mean pressure, exploded at Essone in the Cotton-mill of 
Mr. Eeray, the machine supplied by it was working more 
slowly than usual, and the difference was such as to cause com- 
plaints on the part of the workmen. When the explosion was 



APPENDIX NO. II. 315 

about taking place, the safety valves opened, and vapour escaped 
from them in abundance. 

An accident, similar to that at Essone, took place some time 
afterwards on the Boulevard Mont Parnasse, at Paris. Here, 
as with Mr. Feray, the workmen murmured, because the slow 
motion of the machine diminished their daily quantity of work, 
when all at once the boiler, that they supposed to be almost 
void of steam, burst. This boiler was of sheet copper. There 
was no evidence that the safety valve was in a bad state, and on 
the other hand there is a good reason to suppose, that an 
abundant escape of steam preceded the explosion. 

At the time of the explosion of the steam-boat Etna, at New- 
York, the machine only made eighteen strokes per minute. 
In its usual state of working the number was twenty ; thus then 
the boiler gave way under the action of steam certainly less 
elastic than it was usually customary to carry.* 

The day of the expli)sion of the Rapid, at Rochefort, the 
guage had often indicated an elasticity in the steam of more 
than eleven inches of mercury above the usual pressure of the 
atmosphere. Some seconds before the explosion, the guage 
had fallen to less than six inches of mercury. 

It has resulted from the examination to which the explosion 
of the steam-boat Graham gave rise, that at the instant the 
accident happened, a weight of twenty lbs. had just been taken 
off the safety valve. 

Explosions immediately preceded by the opening- of the safety 

valve. 

I shall first recall to my readers that the explosion of the 
boiler at Essone, might have been classed in this paragraph, for 
the safety valve opened just at the time of explosion. 

A boiler constructed to produce low pressure steam, exploded 
in the midst of a manufactory, immediately after a large dis- 

* Recent inquiries have shown us that one of the three cylindrical boil- 
ers of the Etna, had its communication with the supply-pump cut off, for 
several hours before the explosion ; hence there was a larger space intensely 
heated and filled with the steam generated in the other two boilers. 



316 APPENDIX NO. II. 

charging cock liad been opened, through which the vapour 
began to escape with rapidity. To open a stop cock, or raise 
the safety valve is evidently one and the same thing ; the explo- 
sion in this case, therefore, was determined by an operation 
that it would seem ought to have prevented it. 

This fact, however strange it may appear, must be received 
with the utmost confidence, when I state that I received it from 
Mr. Gensoul, of Lyons, and that in addition, this able engineer 
was an eye witness of it. If, in an extreme case, such as that 
I have just mentioned, the opening of a valve may bring on the 
bursting of the boiler, it must frequently happen that such an 
opening, without occasioning an accident may, notwithstanding, 
give rise to a sensible and sudden increase in the elastic force 
of the vapour. The phenomenon, within such limits may be 
studied without danger. I am aware that the experiment has 
been made at Lyons, and that in a little high pressure boiler, as 
soon as a discharging cock was opened, the safety valve rose 
also. Mr. Dulong and myself, have on the other hand always 
observed that a diminution of tension accompanies the opening 
of the valves. But I do not on that account regard the experi- 
ment made at Lyons as less certain, since it has for witnesses 
M. Tabareau, Director of the School of La Martiniere, and M. 
Rey, Professor of Chemistry. The probable causes of the dis- 
crepancy in these experiments, which I shall point out here- 
after, will show in what manner the particular species of acci^ 
dents that are connected with it, may be prevented. 

Collapsion of Boilers. 

Boilers made of sheet copper or wrought iron, and those in 
particular that work with low-pressure steam, suffer under cer- 
tain circumstances from accidents precisely the reverse of those 
we have hitherto spoken of. 

These boilers occasionally collapse completely, their sides be- 
ing suddenly bent or crushed inwards. The cities of Lyons and 
St. Etienne, have recently been the theatres of several accidents 
of this kind, against which it is necessary to be protected, were 



APPENDIX NO. II. 317 

there no other object than to prevent considerable manufactories 
from being suddenly reduced to a state of inactivity. 

The lesser cylinders that in some cases form internal fire- 
places and flues, also collapse occasionally. Their sides being 
unable, under certain circumstances, to resist the pressure con- 
tained in the circular space that surrounds them, give way and 
flatten suddenly. And as this cannot take place unless the 
metal gives way in some part, the boiling water spreads in tor- 
rents through the adjacent apartments, and often produces 
serious accidents. Mr. John Taylor, F.R.S., has furnished 
the following instance of this kind of accident.* 

At Mold-Mines in Flintshire, there is a large steam engine 
driven by three boilers, with internal furnaces. On a certain 
day, the machine had been stopped for about five minutes ; the 
fireman had already shut the doors of all the three furnaces, 
closed the dampers of two of the chimnies, and was in the act 
of closing that of the third ; but hardly had the metallic plate 
reached its place when he saw a gust of flame dart from the 
fire-place, and an explosion followed instantly. Two work- 
men who were unfortunately in the direction in which the 
boiling water was projected, were instantly killed. 

A close examination of the boiler showed, that the outer 
cylinder had neither moved from its place nor sustained any 
damage. Even the weight suspended to the lever of the safety 
valve, was still in its place after the accident. Neither had the 
less cylinder been moved from its place, but was so flattened 
by the crushing of its sides, that the hand could not be intro- 
duced between the plates. 

It might at first sight be considered strange that I should 
place a crushing of a flue caused by excess of steam by the side 
of accidents of a contrary character ; but it will be soon seen 
that these two different eflfects have in all likelihood the same 
origin. 

* The explosion of the United States, which has just'taken place upon 
Long Island Sound, (September 15, 1830,) appears to belong to this class. 



318 APPENDIX NO. II. 

Accidents peculiar to Boilers with interior furnaces. 

A little reflection on the numerous causes that may bring 
about the explosion of a boiler, and on the various combinations 
of which they are susceptible, will show that is hardly possible 
to obtain invariable rules in respect to them. It may, however, 
be remarked as a general law, that the figure of the boiler is 
the preponderating cause, and that it is upon it that the species 
of bursting that takes place, most frequently Spends. It is in 
this point of view, that detailed and complete accounts of the 
accidents that daily happen, would be of great use. We may 
now assert, in consequence of the valuable investigations pub- 
lished by Mr. Taylor, thatin boilers with interior furnaces or 
flues passing through them, the surface of the inner cylinders 
must be considered as the weakest part. 

After the almost simultaneous explosion of two boilers at the 
tin-mine of Polgooth, it was found, that the inner cylinders of 
both boilers were twisted upon themselves, and torn in a great 
number of places. 

At the mine of East-Erennis, the inner cylinder was not only 
flattened, by the approach of its upper and lower surfaces, but 
had even been thrown out of the building with great force, 
while the outer cylinder had not been moved from its place or 
sustained any important injury. We have already mentioned 
another example still more remarkable, of the complete change 
of shape and breaking of the less cylinder, while the outer one 
remained unaflected. 

Note. — To this list of Arago's may be added the recent fatal 
explosions of the Helen M'Gregor on the Ohio, and ^e Chief 
Justice Marshall on the Hudson. Both of these took place at 
the instant of setting the engine in motion, and in the latter, the 
safety valve was open, and the steam escaping freely by it. 

Arago adheres to the explanation of Perkfllfe given by us on 
page 95, and points out no new means of preverrfj^in besides 
those already recommended in Chap. III. We have not, in con- 
sequence, considered it necessary to translate the residue of his 
paper ; we may, however, quote his high authority in support 
of the views expressed in that chapter. 



Ai?PENDIX No. III. 



List of English Steam-Boats, 



When 
biiilt. 



NAME 



WHERE USED. 



1812 Comet, 

1813 Elizabeth, 

1813 Clyde, 

1813 Margery, 

1813 Glasgow, 

1813 Duke of Argyle, . . 
1813 Orwell,! 

1813 Prince of Orange, . . 
1814Phenix,2 

1814 Eagle, 3 

1814 Richmond, .... 

1815 Caledonia, . . . i 

1815 Argyle, 

1815 Oscar, 

1815 Hope, 

1815 Thomas, 4 

1816 Regent, 5 

1816 Majestic, . . . • . 

1816 Neptune, 

1816 Sir Wra. Wallace, . . 

1816 Albion, 

18l6iEtna,6 . . . . . 
18l7Tug^ 

1817 Defiance, 

1817 London, 

1817 Sons of Commerce, . 

1817 Greenock, .... 

1818 Rob Roy, (now Henry IV. 
1818 Marquis of Bute, . . 

1818 Favorite, . . ■'.' . . 
181.8 Victory 4w . . . . 

1819 Talbot, ^T . • . . 
1819lWaterloo, .... 

! High Pressure. 
3 A Double Boat. 
5 Burnt in 1817. 



Clyde, 

Clyde, 

Clyde, 

Clyde, Leith,& London, Seine, 
Clyde, Thames, .... 
Clyde, Thames, .... 

Ipswich, 

Clyde, 

Norwich, 

London to Richmond, . . 
Clyde, Thames, Rhine, Baltic. 

Clyde, 

Clyde 

New Castle, 

Clyde, 

Thames, ....... 

Thames, 

Clyde, 

Forth, 

Clyde, 

Mersey, 

Forth, 

Clyde, 

Thames, 

Thames, 

Clyde, _ . . 

Glasgow,Belfast,Calais,Dover 

Clyde, 

Thames, 

Do 

Holyhead to Dublin, . . 
Liverpool to Dublin, . . 



Ton- 
nage. 



No. of 
En- 
gines 



25 

40 
69 
70 

74 

60 

40 

25 

40 

60 

102 

88 

70 

45 

72 

112 

90 

88 

95 

92 

75 

95 

51 

70 

80 

70 

100 

59 

160 

160 

156 

210 



Horse 
power 
each. 

4 
9 

14 

14 

16 

14 

6 

4 

4 

6 

10 
14 
32 
12 
3 
14 
12 
24 
20 
16 
22 
20 
16 
14 
14 
20 
12 
30 
14 
24 
24 
30 
2 \ 30 



2 High Pressure ; exploded in 1816. 

4 Made a passage from Glasgow to London. 

6 A Double Boat. 



320 



APPENDIX NO. III. 



When 
built. 



NAME. 



WHERE USED. 



1819 Robert Burns, 

1819 Port Glasgow, 
1819Eclipse, . . 
1820|lvanhoe, . . 

1820 Inverary Castle, 
1820 Britannia, 
I820piana, . . 

1820 Earl of Egremont, 

1821 Majestic, . 
1821 Highlander, 
1821 Tartar, . 
1821 Caledonia, 
1821 Sampson, . 
1821 Venus, . . 
1821 Edinburgh Castle, 
1821 Thane of Fife, 
1821 Union, . . . 
1821 Royal Sovereign 
1821 Meteor, 
1821 City of Edinburgh 
1821 James Watt, 
1821 Swiftsure, 
1821 Hero, . . 

1821 Cambria, . 

1822 Largs, . . 
1822!Lord Liverpool, 
1822| Saint Patrick, . 
1822,Duke of Lancaster 
1822 Prince Llewellyn, 
1822JAlbion, . . 
1822; Cambria, . . 
1822|Hercules, . . 
1822;Lord Melville, 
18221 Union, . . . 
1822 Sovereign, 
1822 
1822 
1822 
1823 
1824 



1824 



Fury, 

Royal Ferdinand, 

Camillas, . 

Soho, . . 

Lightning, 

Harlequin, 



1824 Cinderella, 

1824 Aladdin, . 

1825Enterprize,2 

1826 Shannon, . 

1826 Commerce, 

1826 Amsterdam Exchan 

1826 United Kingdom, 
1827, Dee, .... 

1827 Crusader, . . . 



(Clyde, ...... 

jClyde, 

Thames, 

Holyhead to Dublin, . . 

Clyde, 

Clyde, 

Thames, 

Chichester, 

Greenock to Liverpool, . 

Clyde, 

Holyhead to Dublin, . . 

■Clyde, 

Iciyde, 

iThames, 

jLondon to Leith, . . . 

[Forth, 

jTay, 

.Holyhead to Dublin, . . 
jHoiyhead to Dublin, . . 
London to Leith, . .. . 
London to Leith, . . . 

Thames, 

Thames, 

Liverpool, 

Clyde, 

London to Ostend, 
Liverpool to Dublin, . . 

Liverpool, 

Liverpool, 

Liverpool, . ." . 

Bristol, 

Clyde, ...... 

London to Calais, . . 
Dover to Boulogne, . . 

{ London to .... 

( Boulogne, .... 
Mediterranean,. . . . 



Liverpool ) 

to \ each, 

Dublin, ) 
Falmouth to Calcutta, 

Liverpool to Dublin, . 
London to Amsterdam, 
London to Leith, . 



Ton- 
nage. 



73 

70 

190 

158 

115 

100 

60 

50 

350 

67 

180 

84 

100 

265 

148 

148 

100 

210 

190 

407 

448 

104 

427 

130 

126 

198 
140 
170 
160 
100 
130 
236 
53 



510 
296 

232 

500 
513 
400 
500 
1000 
700 
95 



No. of 

En- 
srines 



1 
1 

2 

2 

2 

2 

2 

2 

2 

1 

1 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

1 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 



Horse 

power 
each. • 



24 
16 
30 
30 
20 
20 
10 
12 
50 
24 
60 
15 
20 
30 
20 
20 
15 
40 
30 
40 
50 
15 
45 
25 
32 
40 
55 
25 
35 
30 
25 
30 
40 
8 
16 
16 

40 
60 
50 
40 
40 
40 
60 
80 
70 
60 

100 

100 
25 



^ The boilers of these boats burst in 1826. 

2 Made a passage between the two ports in 113 days* 



APPENDIX No. IV. 



List of French Steam-Boats existing in 1828, /rom the work of 

Tourasse and Mellet. 











IVo.of iHorse 


When 


NAME. 


WHERE USED. 


Tons. 


En- [power 


built. 






100 


grines. 


each. 


1818 


Le Henri IV 


Calais to Dover, 


30 


1818 


Le Due de Bordeaux, 




Calais to Dover, 


100 




50 


1820 


Le Genie de Commerce, 




Rouen to Paris, . . 


200 




30 


1821 


Le Triton,! 




Havre, 




1 


50 


1821 


Le Havrais, ..... 




Havre to Honfleur, . 




1 


30 


1821 


La Duchesse d'Angouleme 




Havre to Rouen, 




1 


28 


1821 


La Duchesse de Berry, . 




Havre to Rouen, 




1 


16 


1821 


La Ville de Rouen, . . 




Rouen to Paris, . . 


200 




30 


1821 


La Ville de Paris, 






Rouen to Paris, . . 


200 




30 


1822 


L'Aaron Manby, . 






Havre to Paris, . . 


140 




28 


1823 


La Ville du Havre, 






Havre to Rouen, 


326 




50 


1823 


Commerce de Paris, 






Havre to Paris, . . 


160 




50 


1823 


La Seine, . . . 






Havre to Paris. . . 


160 




50 


1823 


Le Charles X. . . 






Havre to Paris, . . 


160 




50 


1823 


L'Hirondelle . . 






Havre to Paris, . . 


160 




50 


1823 


La Caroline,^ . . 






Cayenne, .... 


200 




50 


1823 


Le Coureur,2 . . 






Rochefort, . . . 


200 




80 


1823 


Le Rapide,2 . . 






Rochefort, . . . 


200 




80 


1823 


L'Africain,2 . . 






Sennegal, .... 


180 




32 


1823 


Le Voyageur,2 . , 






Rochefort, .... 


180 




32 


1824 


Le Due d'Angouleme, . 




Havre to Rouen, . . 


326 




50 


1824 


Le Remorqueur,3 . . 




Havre to Rouen, . . 






80 


1824 


Le Commerce du Havre, 3 




Havre to Rouen, . . 






80 


1824 


Le Commerce d'Elboeuf, . 




Rouen to Elboeuf, . 


150 




24 


1824 


Le Dauphin, 




Rouen to Elboeuf, . 


200 






1824 


L'Etna, 






Rouen to Paris, . 


110 




40 


1824 


Le Parisien, . . 






Paris to St. C'oud, . 


65 




12 


1824 


La Parisienne, . . . 






Paris to St. Cloud, . 


QS 




12 


1825 


L'Atalante, . . . 






Rouen to Par,s, . . 


110 




40 


1825 


La Seine, .... 






Paris to Montreau, . 


80 




16 


1825 


L'Yonne, .... 






Paris to Montreau, . 


80 




16 


1825 


L'Ocean, . . . 






Lyons to Givors, 






30 


1825 


La Mediterranee, 






Lyons to Givors, 






30 


1826 


L'Aigle, .... 






Rouen to Paris, . . 


120 




40 


1826 


La Foudre, . . . 






Rouen to Paris, . . 


120 




40 



lATow-Boat. 
3 Tow-Boats. 



2 Tow-Boats, belonging to the French Government. 

41 



322 



APPENDIX NO. IV. 



When 
built. 



1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1826 
1827 
1827 
1827 
1827 
1827 
1827 
1827 
1827 
1827 
1827 
1827 
1827 
1827 
1827 
1828 
1828 



NAME. 



La Dauphine, » ... 
La Ville de Sens, 2 . . 
L'Hirondelle, .... 
Le Courier, .... 
Le Louis Gaibert, . . 
Le Fran9ais, .... 
Le Remorqueur, . . . 

Le Maine, 

La Loire, 

Le Nantais, .... 
Le Lyonnais, .... 
Le Chalonnais, . . . 
Le Mercure, .... 

Le Triton, 

Le Dauphin, .... 
Le Neptune, .... 
Le Serpent, 3 . . . . 
La Ville de Nantz, . . 
La Marie Therese, . . 
L'Ingenieur, . . . . 
Le Telegraphe, . . . 
L'Estafette, . . . . 
La Confiance de Sully, . 
Le Lotte et Garonne, . 
Le Realais, .... 
Le Nageur,4 .... 
Le Souffleur,4 . . . 
Le Pelican, 4 . . . . 
Le Reniorgueur,5 
Le Voltigeur, .... 
Le Marmandais, . . . 
Le Bordelais, .... 
Le Fran9ais, .... 



WHERE USED. 



Passy to Bercy, . . 
Paris to Melun, . . 
Rochefort to Saintes, 
St. Malo to Dinan, . 
Nantes to St. Nazain, 
Nantes to Paimbceuf, 
Nantes to Paimbceuf, 
Nantes to Angers, . 
Nantes to Aiigers, . 
Angers to Chinon, . 
Lyons to Chalons, . 
Lyons to Chalons, . 
Lyons to Chalons, . 
Lyons to Chalons, . 
Lyons to Chalons, . 
Lyons to Chalons, . 
Sennegal, .... 
Nantes to Orleans, . 
Bordeaux to Pouillac, 
Bordeaux to Pouillac, 
Bordeaux to Pouillac, 
Bordeaux to Longon, 
Bordeaux to Longon, 
Bordeaux to Longon, 
Bordeaux to Longon, 
Sennegal, 
Sennegal, 
Sennegal, 
Rhone, . 
Rhone, . 
Bordeaux toMarmande 
Bordeaux to Roy an, 
[Bordeaux to Longon, 



Tons. 



No.of 
En- 
gines. 



Horse 
power 
each. 



60 
50 
75 
60 
70 
65 
124 
65 
65 
55 



180 
60 

220 
70 
70 

86 

86 

86 

500 

500 

500 



190 

86 



30 
12 
12 
10 
12 
12 
40 
10 
10 
12 
30 
30 
30 
30 
30 
30 
40 
10 
32 
12 
12 
16 
20 
20 
20 
160 
160 
160 
30 
30 

40 
24 



Rotary engine, has not been successful. 



3 Government Tow-Boat. 
4 Tow-Boats belonging to the French Government. 



2 High Pressure. 



5 Tow-Boat. 



Note. — As has been intimated in th« body of the work, a list of American steam- 
boats will be published as a supplement. Those on the Mississippi and its branches 
alone, are said to amount to upwards of five hundred. 



APPENDIX No. V. 



Table of the Dimensions of English Double-Acting Condensing 

Engines. 



Nominal 
Horse 
Power. 


Diameter 
of Piston 
in inches. 


Length 
of stroke 
in feet. 


Number 
of strokes 
per minute. 


Velocity 
of Piston 
in feet. 


Coals burnt 

per hour 

in lbs. 


1 


6.0 


1^ 

■* 3 


50 


166| 


20 


2 


8.3 


2 


43 


168 


27 


4 


11.6 


21 


24 


170 


55 


6 


13.9 


3 


31 


185 


73 


8 


15.9 


3i 


27 


190 


84 


12 


19.2 


4 


24 


192 


117 


16 


21.75 


4i 


22 


198 


140 


20 


24. 


5 


20 


200 


166 


24 


26.1 


5| 


18 


200 


187 


28 


27.8 


H 


18 


200 


207 


32 


29.5 


6 


17 


204 


227 


40 


32.6 


6^ 


16 


208 


268 


50 


36. 


7 


15 


210 


310 


60 


39.2 


^ 


14 


210 


354 


70 


42.0 


8 


13 


208 


406 


80 


45.0 


8 


13 


208 


448 


90 


47.5 


'^ 


12 


204 


504 


100 


50. 


8| 


12 


204 


555 


120 


54.7 


9 


11 


198 


660 


140 


59. 


9 


lOf 


197 


770 


200 


70. 


10 


9i 


191 


1100 



APPENDIX No. VI. 



Table of the Dimensions of American High Pressure Engines, 



Nominal 
Horse 
Power. 


Diameter 
of piston 
in ioches. 


Length 

stroke in 

feet. 


Number 
of strokes 
per minute. 


Velocity 
of piston 
in feet. 


6 


7 


2 


40 


160 


8 


8 


31 


38 


190 


12 


9 


3 


35 


210 


14 


9i 


3| 


321 


224 


16 


10 


3i 


32| 


224 


20 


11 


4 


30 


240 


|L. 








_i 



The estimated horse power of the Engines given in the two 
foregoing tables, falls short considerably of what they would be 
rated at according to tte rule on page 138. It would approach 
more nearly to the result given by using 44000 for a divisor, 
instead of 33000, but does not exactly coincide with it. In 
truth, no rule can be given that is of universal application, for 
the friction will vary with the size and proportions of the en- 
gines. It is only in the larger class of condensing engines that 
the effective pressure amounts to that at which it has been as- 
sumed on page 138, say 10 lbs. per inch ; but in one recently 
tested in Cornwall of 80 inches in diameter, the effective pres- 
sure has been found as high as 10.15 lbs per inch. 

The above tables are, however, useful, inasmuch as engines 
are rather classed by their size, than by the actual work they 
perform ; thus the engines of the North- America that have been 
stated to be capable of exerting a power of 186 horses each. 



326 APPENDIX NO. VI. 

and which working at an ordinary speed, have been estimated 
at 98 horse powers, would, according to the estimate of Eng- 
lish engineers, be rated at no more than 80 horses each, and in 
comparing her performance with those of European steam- 
boats, the latter is the number that should be made the object 
of the comparison. 



THE £NI>. 



INDEX. 



Page. 

Air- Valves, 91 

Air-Pump, 153 

Air- Pump Bucket, .... 153 

Ash-Pit, 57 

Atmospheric Engine, . . . 189 

Attraction, 10 

Attraction of Aggregation, . 10 

Barometer, 25 

Beighton, 222 

Bell, 288 

Bernouilli, 279 

Boilers, 67 

Do. materials of, ... . 68 
Do. shape of, .... . 69 
Do. strength of, . . . 71, 75 
Do. surface of, .... 71 

Do. proof of, 85 

Bolton, ....... 236 

Brancas, 205 

Carbon, 50 

Cardan, 233 

Cartwright, . . . 151, 251 

Centre of Gravitjr, . . . 11,15 

Do. of Oscillation, . . 11,16 

Do. of Percussion, , . 11, 16 

Do. of Gyration, . . . 11,17 

Chimneys, 45, 62 

Cistern, Hot-Water, . . 133, 155 
Do. Cold- Water, . 133,155 

Cock, Four Way 183 

Component Forces, . . 12, 14 

Combustion, 43 

Conducting Power, table of, . 39 
Condenser, . . . 117,132,152 
Condensing Engine, double, 

110,141,245 
Condensing Engine, single, 189, 239 
Condensation, Water of, . . 157 
Conical Pendulum, 134, 162,249 

Crank 124, 158 

Cylinder, 116,147 

Damper, 64 

Damper, Self-acting, . . 64, 94 

D'AuxiRON, 279 

Delivering-door, 155 

Density, 21 

Densities of Water, Table of, 30 
Densities of Steam, Table of, 35 
De Garay, 277 



Page. 

De Causs, 235 

Division of Natural Bodies, . 9 
Double Condensing Engine, 

110, 141, 245 
Dundas of Kerse, .... 285 

Eccentric, 136, 159 

Elasticity of Steam, Law of, 34 
Do. Table of, 34 

Engine, Atmospheric, . . . 189 
Do. Double Condensing, 

110, 141, 245 

Do. High Pressure, . . 177 

Do. Single Condensing,188,239 

Engines acting expansively, . 168 

Engines, Rotary, .... 256 

Eolipyle, 200 

Evaporation, 33 

Evans, 254, 285 

Expansion by Heat, ... 26 
Do. of Solids, .... 26 
Do. of Liquids, ... 26 
Do. of Gases, .... 27 
Do. of Metals, Table of, . 29 
Do. of Water, .... 29 
Explosions, cause of, . • . 96 
Do. Precautions against, . 101 
Feeding Apparatus, ... 81 

Fitzgerald, 242 

Fitch, 281 

Flame, 44, 47 

Fly- Wheel, .... 125, 158 
Forms in which bodies exist, 11 

Forces, 11 

French, 256 

Fuel, 49 

Fulton, .... 283, 285, 286 

Furnaces, 57, 59 

Fusible Metal, Valves of, . . 99 

Gainsborough, 235 

Generator of Perkins, . . . 107 
Governor, . . . 134, 162, 249 

Grate, 57 

Guage- cocks, 80 

Guage, Steam, 92 

Guage, Vacuum, .... 133 

Hand- Gear, 222 

Hautefeuille, 211 

Heat conducted, 38 

Heat, Latent, 32 



328 



INDEX. 



Fag's. 

Do. Radiation of, ... . 37 

Do. Specific, 30 

Do. of various fuels, . . 51, 54 
Hero of Alexandria, . . . 199 
High Pressure Engine, , . 177 
High Pressure Steam, . . . 179 
History of Steam Engine,Early, 195 

Do. of do. concluded, 227 

Do. of Steam Navigation, 276 

Do. of Locomotion, . . 297 

Horse Power, 137 

hornblower, . . . , . 251 

Hulls, 278 

Hydrogen, 50 

Injection-Cock, . . . . . 156 

Jacket, 142 

JOUFFROY, 279 

KiRCHER, 206 

Lever Beam, 130, 157 

Leupold, 224 

Livingston, 284, 286 

Machines, Principles of, . . Ill 

Mathesius, 234 

Miller of Dalswinton, . . 282 

MORLAND, 211 

Motion, species of, ... . 17 

Do. of fluids, .... 18 

Murray, 253 

Newcomen and Cawley, . 218 

Oxygen, 43, 44 

Packing, 136, 151 

Do. Metallic, 151 

Paddle-Wheels, 265 

Papin 211,217 

Parallel Motion, . . . 120, 157 

Perrier, 279 

Piston, 117, 149 

Plug-frame, .... 159, 222 
Porta, Baptista, .... 234 
Power of Engines, .... 137 

Power, Horse, 137 

Potter, . 222 

Pressure of Fluids, .... 19 

Do. of the Atmosphere, . 23 

Prince Rupert, 278 

Proof of Boilers, ..... 85 
Properties of bodies, ... 9 

Do. of Fluids, ... 18 

Puppet "Valve, 146 

Radiating Power, Table of, . 38 
Resultant of Forces, . . 12, 14 

RoBisoN, 229 

Roebuck, 233 

Rotary Engines, ^56 

RUMSEY, 281 

Sadler, 251 

Savary, 212,276 



Page. 

86 

222 

143 

,189,239 

143 



of 



224 

21 

22 

30 

31 

283 

34 

35 

92 

105 

115 

135 

179 

260 

276 

262 

260 



Safety Valves, . . 
Scoggan of Potter, 
Side-pipes,* . . . 
Single Condensing Engine 
Slide Valve, . . . 
Smeaton, .... 
Specific Gravities, . 
^''^^9^ Do. Table of, 

Specific Heat, . . . 

Do. Table of. 

Stanhope, Earl of, . . 
Steam, Elasticity of. 

Do. Density of, . . 
Steam- Guage, . . , 
Steam-Pipes, .... 
Steam, how applied, 
Steam-Valves, . . . 
Steam, High Pressure, . 
Steam Navigation, . . 

Do. History 

Steam-boat Wheels, 
Steam-boats, Theory of. 

Do. Table of Velocities of, 274 

Do. Rules for, ... 275 
Steam-boat Engines, . . . 275 
Steam Carriages, 293 

Do. History of, 297 
Stevens, John, . . 283, 284, 289 
Stevens, R. L., . . . 290, 292 
Stewart and Clark, . . . 242 
Sun-Planet Wheel, .... 245 
Symington, .... 282, 285 
Thermometers, 26 

Do. for boilers, . 99 

Throttle-Valve, 135 

Trevithick, 255 

Tumbling-shaft, 159 

Vacuum-guage, .133 

Valve, Throttle, 135 

Valves, Steam, 135 

Valve, Slide, 143 

Valve, Puppet, 146 

Valves of Fusible Metal, . . 99 

Valves, Air, 91 

Velocity of Steam, .... 87 
Velocity of Steam-boats, Table 

of, 274 

Washborough, 244 

Watt, 228 

Watt's first experiment, . . 229 
Do. first engine, . . . 234 
Do. single engine, . . . 239 
Do. double engine, . . 245 

Wilkins, 206 

Wilkinson, 237 

Woolfe, 253 

Working-beam, . . . 130, 157 



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